i have had a subscription to LoveFilm (previously called ScreenSelect) for about a year now.
I mainly order DVDs but have had the occasional game. I would suggest only using it for games if its for -
a) Seeing if you like a game before buying yourself
or
b) Hiring short games / multiplayer games that you dont intend to keep long
The only problem with renting games is that if it's a long game then you end up having them for a long time in which case you might as well buy it. Because of this i've only ever rented games for max 1 week.
In general i've never had any problems with LoveFilm, they always have a great selection, and delivery is usually good. No contracts to tie you down and you can cancel anytime. They are usually always doing deals too, so you can usually get a month or 2 free (or something similar)
Hope that helps a bit.