Just another noob expressing his opinion, I am sure I carry a lot of weight here
There are a substantial amount of us first gen iPhone users here that never upgraded. You don't see or hear from us that much because of the "OMG I just got a 3G phone yipee" threads (which is to be expected), but if you look at the polls you will see a great many of us never upgraded. But there is a hardware difference between the two and it is significant, and it makes it hard to differentiate who it talking about what. This will get worse when the 3G is hacked and jailbroken.
While it may not be the greatest idea to make a 3G forum all on it's own, a different arrangement of sorts should not be ruled out because it is going to become harder to muddle through the mess on who is talking about what in the hacks area especially.