I did a quick check and he seems to be taking heat mostly for shoddy rebuilt injection pumps (also supplied by Rothenbacher, apparently). I saw reviews of other 'hard' parts, cam gears and glow plugs included, and they seem to be positive.
EDIT: Check that last comment. I later found this thread:
http://forums.tdiclub.com/showthread.php?t=269676
Suggests the GPs are Taiwanese manufacture and may be identical to Beru (?).