what's so special about the GS2?
The fact that it's pretty much a unparalleled jack of all trades. It does everything i could want a smartphone to do, but more importantly, in nearly every category it is the best at it.
Other than niggles such as the camera not quite being the best on the market (but still outstanding) and the build quality, while more than strong enough, not being up there with the best, everything else is just top notch.
If you can stretch to a 24 month contract you will easily find it for £25/month, there's a chance of getting it for 18 months at that price if you wait for a good deal. Good deals for this come every couple of weeks or so.