As an iPhone 3G user previously, this is probably a very good thing. The iOS 4.0 update basically bricked the phone because it just couldn't handle it. I recently found out how easy it was to revert to 3.1.3 and its actually a pleasure to use again (albeit still noticeably slower than my 4S).

If Apple released iOS6 for the iPad 1 you would probably be bagging them out for making the device so slow.