The RP350 has been pretty awesome and I haven't been able to use but about 50% of it. It allows the signal of the guitar to be processed a dozen different ways. Want to sound like AC/DC? Punch in number 15. Is that U2 your wanting? That's number 9.
It comes with something like 70 preset 'sounds', including effects and different cabinets. So yes, my 25w Spider Pro-Line practice amp can take on the rich tones of a Marshall. Pretty cool, eh? There's also the software that allows me to create my own 'patches' for different sounds. Haven't even fired that up yet. Of course, you can model them on the fly and store to the device, but the software allows you to pull in patches that others have created. There's a pretty active user community support it. Since the device supports USB, its very easy to record and lay tracks using Audacity. This was something that I struggled with for a while, but now its a snap.
Still working on my strumming and keeping a beat. Its a lot tougher than I ever remembered it being (either that, or I certainly wasn't as good as I remember!). I do think I'm getting up there where jamming with others will help speed the process along.