I got the PS2 version for Christmas in 2001 while I got the PC version as a gift from my grandad the following year. He didn't know I already had it on PS2 but I found it useful several years later.
Having just looked at the Rayman Arena trailer thing found at Pok2's site, all I see different is the HUD which looks more cartoony, and I'm sure I saw a few baby Globoxes in the race courses. And the generator things in Lum fight are different too.
Here's Dark Globox, for anyone that hasn't seen him yet.
To me, it just looks a lot better than the first one, and that alone is enough for me. The stages seem slightly different and appear to have more routes through the stages. It's been a while since I've played.
aaaaaa I can't play Rayman M on PC anymore. Everytime I try to load my game it crashes. I'm also trying PS2 emulation, and while Rayman M is playable my computer's shit; I can't even run ePSXe here, let alone PCSX2.