my 2p.
I bought (swapped) my car privately, and whilst I wouldnt normaly tune a car - it already had the Awesome GTI APR remap.
I have to say, having driven both, I think it is well worth the 600 or so it cost (not me!). I'm told it is around 240hp, but the torque is up too.
Contrary to what I was expecting, the car has better pick up lower down, and really flies. The icing on the cake is the fuel economy is slightly better - my car is averaging just over 29mpg since I got it - and easily into the mid 30's on a motorway run...