On the other hand, the rollover minutes are a godsend when you are on the phone a great deal only once in a while.
Most months I barely use my minutes, using about half of my 450. In April I busted my knee, in May I had surgery. Between doctors appointments, updating my parents and girlfriend, and spending essentially almost two weeks in bed, I burned through all my month's minutes and ate into the rollover. Not by a ton, but I was glad I had the excess.
Most postpaid plans aren't going to be much cheaper than AT&T's for 450, and rollover might be gimmicky but it has the potential to save you some serious cash.