Here’s some great advice from Marco Arment about buying products that are great on Day One, instead of buying and simply hoping that software updates will make your product useful in the long term:
I never make technology-buying decisions based on future promises, rumors, or potential. I let other people be the bleeding-edge extremely early adopters, and I stick with what I know will work and stay out of my way.
I think this is really sound buying advice. The only time I really warn people to wait for a newer model (and not buy something right now) is when I know something way better is just around the corner. Upgrading to an iPhone 4S within a month or two of the new iPhone is one such situation – especially given the ridiculous three-year nature of many Canadian cellphone contracts.