I'm doing it now (A2). Got an A in the first year, somewhere around 90%. Predicted an A/A* this year. Also on for an A* in core maths. I find the core maths ridiculously easy, but the further maths is a challenge once you get to some of the more difficult questions, especially on the FP2 paper. I'd say it's worth doing if you found GCSE maths really easy, and did well effortlessly. If you had to put a bit of work into that, then maybe it's not for you, but it's worth a try either way.
I've applied for maths at Cambridge, Warwick, Manchester, Bristol and Nottingham, Warwick, Manchester and Nottingham, and an interview at Cambridge early next week. Still waiting on Bristol, but it's not going to be one of my choices anyway.