I just downloaded this last night and three of us had a quick go - we were very impressed.
Tried all the modes at least once, I think the crown one was our favourite but they're all good. Managed to unlock the miis as well which was cool.
We also tried it online and it worked really well, 3 of us and 4 randoms fighting it out. We had to wait a bit whilst playing the bomb dodging mini-game but probably wasn't more than a couple of minutes. I don't know why it has that ".. player game is available" message, it makes you think you need to do something to connect to it but I think you are just supposed to wait and let it sort it out.
It's great that it supports 8 players on one console too, I've got 4 wiimotes and 2 gamecube controllers so I'm already set up for some 6 player offline games. All in all, this is an absolute bargin for £7!