No not at all... Look at the 3G and 3G which one would you rather have? Sure if you have a iPhone 4 you might not want to upgrade I understand that and respect that, but if you skip a generation like I do you get the faster version of the model you "missed out" on. In short: You should get the iPhone 4 if you have a iPhone 3G or below.
Mate, while the 4S looks good and is slightly enhanced from the current iPhone 4, just stick to what you have and wait for the iPhone 5. I expect the 5 to be released some time next year, maybe by mid-2012, who knows?
If you have an iPhone 4, an upgrade to the 4S isn't really necessary. If you didn't have an iPhone before and this is your first time, like me, it's an awesome update.