Re: Loop!
I have several loopers (Boss RC-2, Boss DD-20, Line6 DL4, and Oberheim Echoplex Digital Pro)...every show I play, either solo or with a band, has some sort of looping going on.
It really depends on how you use it. The RC-2 is great for practice, and small enough to carry anywhere. If you want to just record some chord progressions and solo over them, I recommend that one. The Boss loopers (RC-2/20/50) all suffer from some bizzare design decisions that make some functions just plain weird to get to, though.
For live layering of loops and using them as improvisations, none of the Boss Loop pedals have variable feedback (the big deal-breaker for me), which allows the old loop to gradually die as new stuff is being added. The DD-20 Gigadelay can do that, but you have to preset the loop time. The DD-20 is great for inserting non-rhythmic loops in a song though...I do this all the time.
The Line6 DL4 is my choice for live looping with acoustic guitar, since you can vary the volume of the loop with an expression pedal- you can do fade outs (it doesn't stop right away like the Boss pedals) and start a new loop over top. The DL4 is really the most intuitive looping pedal out there- looping time and the ability to save the loops mean nothing without control over them (to me).
The Oberheim Echoplex is a rack unit that I use with my electric- which probably allows for more control over a loop than most people ever need.
Check out this chart too:
http://www.looproom.com/looperchart.php