I am on my third MK6 GTI (all DSG) and they have been very reliable and great cars. There is a lot of info on here about various problems people have had with their GTI's such as rattles, paint quality, DSG
Mechatronic issues etc etc.
However I must be very lucky as I have had none of these issues with mine. My MK5 did chip badly and it rattled too but managed to cure that. Overall these are really good cars but with everything nothing is perfect and they are mechanical an eventually something will go wrong.
If you want one go for it I would recommend the ED35 over the std GTI as is better equipped in std trim and has the old engine with the K04 turbo which feels quicker and a bit more exciting. However it's not as good on petrol consumption as the regular GTI.
Good luck