If I was eligible, I would strongly consider uprading. We got our 3Gs in October. However, since I am not, I don't think it's worth the extra $200 right now.
It's gonna suck for a year, listening to you all talk about the exciting new 3GS features, etc... but...
Next summer, I'll be thankful I waited!!! Who knows what's in store for the next iPhone. And if there isn't a new iPhone, then perhaps I'll get the 3GS depending on everything I hear throughout the year.
So, yeah, I'm gonna wait, but part of me wishes I could get the 3GS... oh well...