Like so many companies with well established brand recognition, they are now selling lower quality products and riding on the brand name. This is true in part, especially with their low-end products like the "classic". (The classic goes on sale from Target for $150).

Another part of the game is that they have a wide product range. Their high end mixers are (at the time of this writing) still made in the USA and have a good reputation for having a bullet-proof warranty. The low end mixers are made "offshore" and may have plastic gears.

Plastic gears have a couple of virtues. They are cheap, which lets the company sell (and you to buy) a lower cost product. They are also very quiet. Under heavy use, they fail and the word is that even within the warranty period KitchenAid will claim you are using the product for commercial purposes and refuse to honor the warranty.

The Classic This is their "entry level mixer". It has a MSRP of $330, but you can find them on sale at places like Target for $150. Might be just fine if you were really sure it would only receive occasional light use. It has a 250 Watt motor and a tilt head. It has a "8 cup flour index".

The Artisan Some people love their "Artisan" models, which are a step up from the entry level "Classic". Like the Classic it has a tilt head, which some people find handy and prefer. MSRP is $460 (but often sells for around $340). Many colors are available. It is the same size and looks identical to the Classic. The main difference is that it has a more powerful (325 watt) motor. It has a "9 cup flour index". There is also a model called the "ultra power" that looks (to me) identical to the "Artisan".

Beyond the Classic and Artisan, you get into what they call their "Professional" models, which have more powerful motors, metal gears, and are made in the USA. Typically the Professional models also have a rigid head and a bowl-lift mechanism, which many people find less convenient than a tilt-head, especially when you need to add ingredients to a mixture.

The KitchenAid Professional 5 Plus. I had selected this model as the one for me, but then found some great deals on refurbished units of a nearly identical discontinued model (see below). It is made in USA, has a metal drive train, and is a "bowl lift" rather than a tilt-head model. I see it selling online for $280 to $320 with free shipping. It is 16.5 inches high, so it should just fit into the 17 inch clearance under my cabinets. Unlike a tilt unit, it does not need extra clearance for when it tilts. It has a 450 Watt motor.

The KitchenAid Professional HD. When I found refurbished units for $199, I placed an order for one of these -- direct from KitchenAid (Whirlpool). Like the Professional 5 Plus, it is a bowl lift mixer, with a 5 quart capacity. It has a 475 Watt motor, slightly more powerful than the Professional 5 Plus. They give it a "12 cup flour index". As a refurbished model, it has a 6 month warranty rather than a 12 month, so it will be important to use it regularly as soon as it arrives. Also note that if you peek inside to find out if your mixer has a plastic or metal gear frame, you will void your warranty (if they find out).

I found a review on Amazon where a fellow describes rebuilding his Professional HD after he found it had a plastic gear support housing inside. This was from "JG" in October of 2009. Hopefully KitchenAid (actually Whirlpool) is no longer shipping units with plastic frames. I guess I will find out.

The recommended pouring shield for the Pro 5 Plus is the KN256PS, and it remains to be seen if this fits the Professional HD also. The pouring shield is a recommended accessory, as is an extra bowl (K5ASBP for $46.20). The attachment many people like is the grinder.

Hello everyone. I purchased this mixer just a few years ago, and I just had to do a COMPLETE tear down and rebuild. Yes, it has all metal gears and metal bearings inside. Unfortunately, it also had (repeat HAD) a plastic housing holding all of that metal gearing in place. Yikes. Bad. When I got a little aggressive with the grinder attachment, the 475 watt motor was strong enough to destroy three steel gears and the plastic gear housing that once held it all in place. Fortunately, the mixer is VERY easy to dissasemble and repair, although it took me four evenings of work to assess the damage, clean, and reassemble. I have replaced ALL the gears and bearings with newer versions that you can find online. All the parts I ordered were very reasonably priced ($3 - $18), labelled made in the USA, genuine Whirlpool, and many appear to be upgraded, ESPECIALLY the all metal gear housing complete with cooling fins. Awesome. Total price to replace all of the gears and bearings, including the whole planetary assembly was $110.00. That's much less than a new one, and I have all the latest improved parts. This time I know it is done right. I was VERY disappointed to find upon dissasembly that NO grease had been placed in the top bearing. It was running dry since the day it was new, and it was scored. Due to poor lubrication, all the other bearings had worn, and the gears were meshing loosely. The orbital planetary assembly also had no grease in its sleeve where the beater attaches, and the sleeve bearing and was worn. A lot of the grease in the plastic gear housing was hardened and not doing its job any more. Dissasembly was very disappointing. I say SHAME on KitchenAid for advertising it as all metal gearing and then not lubricating those bearings and then using a plastic housing to hold it all in place. The new parts and the overhauled mixer are very pleasing. I now own the best.

Tips: Parts and diagrams are available online. Shop for low parts prices, which vary by 500%. You will need a special pin-spanning tool to remove two very strong "c" clips and I recommend a square-point drive screwdriver. Special grease that is USDA approved "H-1" for food preparation use is available online or locally. I bought Super Lube brand at my local hardware store for a few bucks. Be sure to remove ALL of the old grease. ALL of it. Lubricate every bearing twice during assembly to make sure it has grease completely coating the inside of the bearing. If you buy a new planetary assembly, (why not do it all at once so you never have to do it again) take the "c" clip off and grease the beater drive shaft. The bottom bearing for the main shaft is pressed into the mixer housing, but it can be pulled out gently with a large pair of pliers. The new bottom bearing should be very gently tapped into place with a hammer - I padded my hammer with about 10 layers of paper tape to protect the bearing - go slowly and gently. It went right in. The motor still is very loud, with a high pitched whine, but it always has been that way and it is 475 watts, so I expect some noise. Do yourself a favor - do a little research, find the new parts, get the "c" clip tool, and rebuild yours with all the new parts. Then and only then can I recommend this mixer.

Another person (Ira Carmel) did the following to their mixer:

As I mentioned, the head can also loosen if you are mixing a large amount of tough materials, such as ground sausage. I eventually fixed this head loosening problem by taking the mixer apart, and replacing the philips cross head screws with allen head hex screws and lock washers and bolting it town more securely.

I have also performed lash adjustments on the motor positioning after a year of use to make the motor less grindy sounding. This worked well, and I found that this mixer does have a strong metal gear set in it to which I applied fresh lithium grease.

Beyond these 5 quart "professional" mixers are the 6 quart "Professional 600" which is bigger yet, and the 7 quart "commercial" mixers with 16 cup flour index and NSF listings (which I guess lets them meet health requirements in restaurants). These are more than I want to consider.

Some people say to forget KitchenAid and buy a Bosch mixer. And they may be right. The Breville 5 quart looks interesting for $300. A unique feature is a built in timer.
Viking and Cuisinat are other brands that get mentioned.
Take a look at this review of the Bosch Universal (not a stand mixer, but interesting).

It looks like both Bosch and KitchenAid both offer 1 year warranties, although I am seeing mention of a 3 year warranty on the Bosch motor.