I have the RP350. It sounds great for just about anything but super high gain metal. With the 2101 model, I get something very usable though. If you like metal from a pedal sort of tone, then those will definitely suffice.
But I personally have had better luck with some of the free software modelers.
The FX are great and it makes an excellent all-in-one practice tool and for recording scratch demos. It is also great for experimenting since you have a whole palette of stuff to play with.
But anything more serious and releasable, I would only use it for monitoring the DI tracks for low latency. Then re-amp the DI tracks either with VST's or real amps.
For live use, I tried to use it for a festival show (shared gear) and spent a lot of time dialing. But I couldn't get it quite right for high gain. Either it was too harsh, or didn't cut. In the end I ended up using a Sansamp GT-2.