I've got a ChippedUK ST3 on mine. No problems with it or ChippedUK myself but I've heard stories.
The car drives fine, I doubt very much it's as powerful as some re-maps having had plenty of others over the years, but it's smooth and does the job.
I admit I only got mine because they wanted a mk5 guinea pig so it was much cheapness but I don't have any complaints.
There are plenty of tuners out there with good reputations, my advice would be to see which one is doing the best deal when you've got the cash to hand.
I've used REVO, UPsolute and AmD in the past with no problems and they all do what they are supposed to.