iPhone4 - good; iOS4 - mediocre (at least on iPhone 3G)

Whilst iPhone4 is getting rave reviews, the iOS4 update for older devices, notably iPhone 3G, is not so good.

The advice? If you are on iPhone 3G and haven't updated yet, you definitely want to read up on other people's experiences first and hope Apple release a patched version of iOS4 soon. I don't think we'll be seeing any feature enhancements though. That'll teach us for being 2 hardware versions behind...