About seven years ago I bought some full cell Pierco frames (about 20)
to test them out.  They work fine, the bees use them over and over just
like natural comb, and they are extremely easy to uncap either manually
or with an uncapping machine - just scrape right down to the cell tops!
 
However, as with all things, there are a couple of problems:
1) These frames are heavy compared to wood or plastic foundation frames.
An empty super feels like it has quite a bit of honey in it already.
2) In a poor honey flow, the bees sometimes don't fill the cell up to
the top.  Then when they put a capping on top of what they filled, it is
almost impossible to uncap without punching a hole in each and every
sunken cell.  That sure takes time, even using a cappings scratcher to
punch a line of cells at once!
 
Ted Fischer
Dexter, Michigan USA