Anyone else tried the Firgelli actuators?

I decided to spring for one of the expensive Firgelli actuators, and just gave
it a quick try.  I either got a broken unit, or it is the worst piece of junk
anyone has ever made for NXT.  First of all, you command it to move a distance,
not command it to a set location like you would expect for a servo.  OK, I can
live with that, but if I command it to move 10mm, some times I get 7, sometimes
I get 12, sometimes I get 20mm, and sometimes it just goes all the way to the
end stop.  Totally el-flako useless. 

Anyone else had any experience with these things?  Did I just get a lemon?