Yes, it's $179 if you're due for an upgrade, otherwise they try to charge you $350.
I called and told them that I wanted the G1 for $179 even though I wasn't due for an upgrade for 10 months. My family has been with T-Mo ever since they were called voice stream or something, so they were happy to comply.
Depending on how long you have been with them, they might give you the upgrade deal even if you aren't due. The good thing about T-Mobile is they have excellent customer service