Finally I've reached the top.

Author's Rating:

Pros: Most powerful motor available. Slow gear-up feature prevents flour storms. Tough, durable.

Cons: Noisy (sounds like an airplane). Big.

The Bottom Line: 
Buy it, and don't mess around with anything else, if you make dough, cookies, etc., on an almost daily basis.

Author's Review
I make pizza dough nearly every day. (My teenage son won't eat anything else, and I've conceded the fight.) I started (innocently) with a bread machine, and after going through 4 of them, switched to a KitchenAid 5-quart (Artisan) mixer. Ironically, I broke that one while making KitcheAid's own whole wheat bread recipe. The motor just strained, then stopped. I decided to upgrade to the 6-qt. 'Professional'. KA's staff is terrific, and they promptly sent me the new mixer.

I could not be happier with this one since it seems to have the power I require. I am what I would consider a heavy user. I make not only pizza dough, now, but bread often, as well as cookies and assorted other things. It is by far the best kitchen appliance I ever owned, even including a KitchenAid food processor. I got it not for the extra-capacity bowl but for the extra power; I don't make large batches of anything but I find it much easier to add ingredients to the new, bigger bowl, and I rarely if ever use the pouring shield. This machine also has a slow start-up mechanism that prevents splashing and swirling out of ingredients.

I have read others' comments that it is cumbersome since it does not tilt up, and I will admit that sometimes it is tricky getting the dough hook out, but not annoying enough to worry about. If I had to give advice, I would say if you use it a lot, you should go for this machine in the very beginning, instead of being forced to work your way up to it, as I did. It is very large and noisy, but consider it the equivalent of a power tool, which delivers the results you paid for reliably and continually.