4 generations of the iPod Touch and I assume the iPhone. Games in the store that will work great on all, slow on some, with problems on others or great on others. The store will let you buy any game for any machine through iTunes even though it knows what has been connected. Releases here (in TA) make little of any mention of what devices do what. So the marketplace is fragmenting. IPhones may update every year with a contract but the Touch does not. Game updates do not show any information so when a developer upgrades and excludes OS3 / 1st gen as a result you are completely SOL. You paid, you had, you had it taken away. Even if they did you cannot opt-out a game from updating automatically. Some will say we should go buy the latest and greatest at every chance but this is not about money. You can probably own a 4th gen machine yet buy a 1st gen app which will not work. It's getting to be a mess and it won't get better.