The Boss RC-505 is superb!
This unit offers pretty much unlimited looping flexibility and combined with it's ease of operation it really inspires creativity--and I mean that. It's made to be operated by hand mainly, though most of the functions can be operated by footswitches/controllers. The only draw back with that is if you want to play your instrument continously while setting up loops, well, thats not really possible so you have to go the footswitch route.
Sonically, it stands on its own for live performance with really no need for outboard processors--that is, it sounds great and the fx sound very good too. Can insert and imprint fx on the input side and/or add fx to the live output mix, they are NOT loop fx(can't string together)though you can loop an outboard fx prossessor. You CAN imprint an fx on the input side and then add a different fx on the output and switch between 3 fx buttons(options) for live tweaking. It makes sense when you get the thing and use it, believe me and you can edit fx parameters to some degree. It has phantom power.
All 5 tracks can be panned in the stereo field and it all goes thru stereo outputs ONLY. The limit to stereo outs only maybe places some limitations for studio recording, I suppose.
The status LED red/green/yellow light circle around and can be set up to track where you are at in the loop which is a GREAT feature. Once you set up the initial loop track it you can then come in anywhere in the phrase in subsequent tracks which is very convenient and you can overdub onto each track ad infinitum.
Well, I could go on but suffice it to say, the RC-505 exceeded my expectations and is pretty much 'ridiculous' for creative looping. If you can't get it done with this thing, well, you might as well give it up. This unit will inspire any real musician.
My only real complaint is that it doesnt have more tracks, like 8, 12, 16, but hey, I can live with it.