So I was a long time customer of t-mobile (think 10+ years)... but they lost me when they failed to keep with their network and as a result, they lost me to Verizon... so far I can say I am happy with Verizon and I am happy with my storm. It is the best BB I have ever had (this is my 3rd one). I am glad this BB worked out, since I hated the Pearl so much.
As for verizon, I can say I have had far superior service with them, than with t-mobile and I don't regret switching at all.
So add one more vote for Verizon!