@jasongins
The big question is "what do you want to do with it?". The A500 runs an old version of AmigaOS, and is limited in some aspects, for instance, it uses an older Custom Chipset (the part of the Amiga that does graphics among other things) than the more recent models. The A500 is great for retro games, but little else nowadays.
If you do want to do something a little more serious, I'd recommend getting your hands on an A1200 (with a hard drive). Its capable of running far more recent software than the A500, and despite having a smaller case, appears to be easier to expand. You can also get them very cheaply.
If you did get an A1200 then I'd definitely keep the A500 in its box, as it could become fairly valuable.
