I was browsing some more at the KA forum about the Pro600.
Quotes are from this KA thread http://forum.kitchenaid.com/forums/topic.asp?TOPIC_ID=7355
It's a short thread but the first posters story may interest you.
Because bread flour is a specialty flour, it produces a much heavier & dense dough, only 8 cups is advisable.
There were recommendations to break-in the mixer with some lighter load recipes (cake and cookies were mentioned).
In the new 600 series there are all metal gears, which generate more heat than the nylon/metal combo..hence the thermal overload feature. When the mixer turns off, it's because it was too hot. Not to say that the mixer has failed at this point..the thermal overload protection has come into play. Normally the mixer will turn back on after a few minutes rest, in the OFF position.
One thing you might consider when you have the new mixer, is making a few "basic" recipes first. Familiarize yourself with the mixer on cookies or cakes initially..When you're ready to move on to specialty bread recipes, add about 6- 6.5 cups of flour initially, then add the rest about a 1/4 cup at a time..until you "see" the dough is ready. This should take about 2-4 minutes (kneading) total. Please come back and let us know if this helps..sure hope so!
Last week I did a double batch of Steve Quick N EZ NY, and experienced no problems (just under 2 pounds of HG flour but it's a high hydration formula).
I just mixed up DKM/Randy's KA thin crust. I forgot that this lower hydration dough wasn't kneaded, so I have nothing to report. This formula has me very intrigued
It will probably be my Semolina recipe that trips the mixer since it's made with a heavier flour . Ironically, this is the one I use most often.
I'm hoping it won't need the full 8 minutes with the new spiral hook.
I will continue to post on my experiences with the Pro 600.