There is really not much to say.
Gamespot has given this game a very low score, and maybe it's deserved in light of previous games, etc. However, I think that anyone wanting to play a little pool without leaving the house or buying a table (who has that kind of money after buying a 360???), or requiring friends. All of that is built in.
This is not a great value for the XBox Live Arcade. The cost is more than I would like to have paid, and when Gamespot and others give it low scores, the company is not as likely to make back their money. It's still cheaper than buying a disc would have been.
This is a fun game, take a look at the demo and decide for yourself.