I just don't see why
The little console thingy is £70 and buying a game costs the RRP and is unlikely to drop.
For that you're tying yourself to a service that may not last forever and you never actually own your game.
Why not just buy a second hand xBox 360 (I got a 2009 model Elite for £80 last year)? You can then hunt around for the best prices on new releases and pick up plenty of cheap old games. Or just rent them the old fashioned way.
No mention of the subscription fee. Is that still around or did they decide it was silly?