iPhone 3g AT&T, Treo 750 Verizon because:
I love the iPhone BUT....
my family is all IN on Verizon. I was still under contract when I got the iPhone so I have kept the Verizon phone for them, plus to receive and send MMS and videos and txt (we have an unlimited family plan).
And most importantly as said above, my Verizon phone gets reception where AT&T doesn't (those TV commercials of AT&Ts are a bunch of BS). We own a membership at a camping resort which we go every other weekend or so. The AT&T phone does not work there, if I want phone service I have to use my Verizon phone.
When I go to my mom's house AT&T gets no service, Verizon works just fine there. So for all these reasons I have not yet given up my Verizon phone and cannot give up my iPhone. The Storm had me tempted but was not impressed when I saw it at Best Buy today.