Screw Motorola, their phones are so proned to having problems, the T720 is a great example of the crap Motorola is capable of dishing out. Motorola has been around a long time and they have yet to release anything that's worth calling a cell phone. The v551 seems to be the same thing as the v600, why doesn't Cingular carry the v600 anymore?? Because of too many complaints about the thing. What does the v551 have that the T637 doesn't, MP3 ringers? Wooo. I'd trade MP3 ringers for reliability any day.
I have a T637 as a matter of fact I purchased a second one just to have. It is a great phone, reception (Cingular) and battery. My car charger has not worked for months and I am never worried about my battery going dead. The Motorola is a nice product if you need a flip. I bet my right arm on the T637. Stay away from the V220 though.