I haven't been to a lot of the metro phx bike shops, but all of them listed in this article have a good reputation.
http://blogs.phoenixnewtimes.com/jac...p_ten_bike.php
Landis, Bicycle Haus, and Faster all have teams and promote the local races and whatnot. I've also heard great things about Slippery Pig, Rage and DNA.
The only thing, I'd warn you about is the heat in the summer, which makes it a little difficult to commute by bike...mostly in the aspect that if you're going any distance, you might be hot and sweaty when you get there. As long as you have a place to freshen up before a big meeting or whatever, you should be ok.