Well... It's Wario Ware, and I'm sure you know what it is
Adding the Wii-mote and the possibility to play up to 12 persons (I wonder, since I've seen data about 5 players and 16, so I really wonder what the truth really is...)
IMO, this is the 2nd best game out for Wii at the moment (excluding Wii Sports).
I think it's worth getting in case you don't mind a short game (because Wario Ware's longevity is really short) and got the money for it... I just won't buy it 'cos I won't pay 60 euros (nor I have 'em >_>) for a game that short...
But that game must rule in parties with friends