Drizzy,
I believe the early upgrade benefit was only for people who purchased the iPhone 3G in July, Aug or Sept of last year. I'm not sure if it applies to other phones if you don't didn't get the iPhone. Again, you can easily call AT&T or check online at the AT&T wireless website. You just log into your account and then check on your upgrade eligibility status online. Only takes about two minutes to check, and you can see right there if you're eligible for the iPhone 3GS pricing too. It basically gives you a big list of phones you're eligible to upgrade too. If you're too lazy to do that
just call AT&T and ask them. None of us here can tell you 100% if you're eligible or not.
Good luck! I hope you can get your 3GS soon!