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Android ages surprisingly well. There are still millions of 2.3 Gingerbread devices out there, and most apps will work on them unless they are graphically intense games like Dead Space or the like. 2.2 Froyo is down to less than 5% of active Android devices, as reported by Google, so I would not expect developers working on new apps to devote much effort to making sure they work with Froyo.
Even so, many apps will work perfectly well with 2.2. I find the hardware is generally the bigger problem, especially with 2.2 devices. These are from long ago, technologically speaking, and while a slow 600-800Ghz CPU isn't the end of the world, limited storage can be. Some of the older phones have barely more than 100Mb of internal storage, and it doesn't take long to use that. Although, if you are willing to root, you can address a lot of issues to a point, including the option of flashing a 2.3 ROM on a device that was shipped with 2.2.
I have an old Motorola Flipside that runs Android 2.1 - many apps don't work, but I can get to websites. Many run a bit slow, but I don't think it's the Android, as much as the phone, that causes this. I can see videos, although I haven't tried movies. Music is good with it. I don't know about games.