Life gets a little less bright.
Android 2.2 supports tethering, and one of the "traditional" advantages of Android as a platform is the ease with which it allows tethering. While T-Mobile has a history of being rather tether-friendly, the news has dropped that the G2 may be unable to tether at launch. This is based off of an internal memo leaked to T-Mo News.
Since the G1 tethered just fine (thanks, PDA-Net!) this represents quite a shift for the carrier. They did make an official statement, acknowledging that tethering and WiFi sharing will not be initially supported on the G2, but then stating that they recognize the consumer interest in these features and are working on a solution. Whatever that means.