I'm a smartphone holdout, primarily because I'm really against paying a premium for mobile internet when I pay for it at home and sit in front of it all day at work. This is the same price as the plan I'm using now, so unless there's a trap I'm not yet aware of, like T-mobile pulling the rug out a year down the road and I'm left without a plan, I see absolutely no reason not to go for it.
The real reason I want to switch, though, is because I'm so tired of getting phone numbers from chicks and having to preempt them with, "never mind my flip-phone, I do actually have a job in spite of how this may look".