The 6 million Dollar question!
REVO is excellent, delivers on it claims, has excellent after sales, BUT its pricey.
GIAC seems to be at least as good, the other guys on here have good experience and I thinks its bit cheaper than REVO. Seems to be the remap of choice at the minute.
Custom Code come highly recomend in VW circles and they are offerring a massive 30% off at the minute making it very good value.
Superchips do the Bluefin product, its also good value at around £450-£500 (that includes the handset for switching between maps.)
SC are veterans of the tuning game, but there has been a few indifferent reports from guys on here so Im not sold on it to be honest.
They are others, such as MTM, Morego(BBR), CHipped UK, Oettinger, APR.....
Good luck
Paul