Quite expensive. £12 a month expensive (about 14 euros i guess). Shame if it puts you off. It is expensive, but If you don't mind paying for quality it's worth it.
My gaming time being under pressure by a little alien from innerwomb, I'm not going to sprinkle out cash over a game that might or might not turn into a big dissapointment within a month or two, while I prolly won't be able to play much either way.
Hence: yay Steam! and move yer bloody asses with the summer sales!
Anyway, games that I can easily pause or idle for several hours are the way to go atm. LA Noire, Civ5, TW-series. And focus on SP over MP, as I don't feel comfortable having ppl to wait for me. L4D(2) is goodish, as my char will be AI'd when I go idle.