This Infosync article notes that T-Mobile also has a $19.95/mo unlimited GPRS plan. I’m going to stick with my initial 10MB/mo for $9.95/mo until I see exactly how much I use. I’m pretty sure that each additional meg after that is only an additional dollar, so if I go over a little bit, it’s (hopefully) not a big deal.
Another question is what is T-Mobile’s definition of Unlimited? Lets hope it’s not similar to the definition of Unmetered in Ireland.