Oh, and Colloseum had the Masterball Glitch, which if exploited means you get unlimited Masterballs and catching the beasts becomes dead easy.
The final battle is much much, MUCH harder than an elite Four battle, as you dont have an opportunity to heal between each opponent. I remember spending about an hour grinding for levels before trying it... and I think still needing to spend yet another hour or two grinding away before being able to really do it. Since you cant trade between the GBA and GC games until you complete story mode that final battle was a thorn in my side. But well, well worth it.
I also want to add that since the story involves a region in which there are no wild pokemon, and is very Distopian it is an awsome contrast to the largely utopian view in the main series games.