DigiTech RP21d - Looper Mode?

["John McCullagh" <johnmcc@aldiscon.ie>]

Hi all,

I've used a DigiTech RP7 for looping, and it makes a basic, but easy to use
looper up to 3.5 seconds. I was reading the manual for the RP21d off the 
web,
and notice that it has a function called "Sampler" which says "samples can 
be
layered, and may be put in loop mode". This sounds very nice, and appears 
to
have all the parameters of a Boomerang, but it makes no mention of the loop
length anywhere. The "Delay" function specifies 1.4 seconds of memory, but
that's less than the RP7, and not practical for stacking loops! The RP14d
doesn't have this feature, but it does have "Learn-a-Lick" which records 12
seconds of input, and automatically loops it.

Does anyone own one of these, and might be able to describe its usefulness 
(or
otherwise) as a looper?

Regards,
John