Should I switch to T-mobile!?

My contract with ATT expires May 7th, and I am ecstatic! right now me and my mother are on the plan, I pay around 98.00 a month for two lines, one has phone insurance, and we have like 500 minutes, we have LG VUs right now. My original plan was to get the iphone for myself, and my mom a simple phone since she doesnt like anything high tech. but I think it's getting too pricey, and I've heard rumors on CNN that ATT plans to raise their prices again!...what do I do!? Ive been wanting the iphone for 4 years! and I can finally have it! Is the iphone worth it? Is it really that amazing and life altering? or should I switch to T-mobile and get their most expensive phone? i think it's the my touch? for those of you who have my touches and iphones...any opinions!? and what apps does the my touch have? is the iphone worth the price? ANY THOUGHTS!? I'm torn, and don't want to make a mistake that will ruin my life for 2 years.