Which exam board? I sit WJEC, and it's TOTALLY different to GCSE physics. I think it's way more interesting. It kinda follows on from the triple award module I did, with things like history of atomic structure and absorption and emission spectra. I thought it was a lot of mathsy, although M1 overlaps with a lot of the first PH1 module at AS, and M2 overlaps with the PH4 module.
I think it's definitely harder than GCSE, and would say a lot of people find it very difficult. But that's a lot to do with your natural aptitude for Physics. I find Physics a lot harder than Biology, but loads of my friends who study both can't understand this at all!
Would say it's very interesting and useful though! I thoroughly enjoy it!