There was two GBA games, Caliban. Now then, how is it for reply value? More or less the same as Wario Land: Shake It?
I haven't received my copy in the mail yet, but from what I remember of the PS One original, the replay value wasn't too high. You could go back to all of the levels and collect 100% of the gems, which unlocked at least one wicked secret level. But, aside from starting a new game file a year or two later (which was pretty enjoyable), that was it.
However, it looks like this version of the game has some added modes and such that'll extend replay a good bit further. I think $30 seems reasonable, and most of the game will be a retread for me. I suppose it might make for a good, longer rental, though. But if you like good platformers and can spare the full entry fee, I say go for it.