From what I've read it is much better (I'm actually considering replacing my HiTec Spectra module with FrSky for FPV flying). AFHSS is great, but FrSky has some useful features Spectra module doesn't have (you can use external antennae and/or signal amplifier, telemetry feedback includes signal strenght info etc). It seems it's good even up to 4500 m in optimal conditions with directional antenna and even up to 10 km with with signal strength amplifier.
FrSky's technology is actually one of the leading 2,4 GHz technologies on the market right now (competing with AFHSS, FASST, DSMX and DMSS). It's used as a reference technology in Tx reviews... Pretty strange having in mind it's chineese and dirt cheap, huh? ;]