Chiptuned my 08 4.8i last month.
Old 355hp 475nm
New 390hp 515nm

Engine sounds just a little better.
0-100kmh car reacts just a little bit faster (not a big difference -maybe 0.5sec faster).

Biggest difference I feel from 100kmh-200kmh.
The car is much faster, much!
No more top speed limit - when the snow melts will try.

Consumption worse when I floor it, better when I take it easy.
Average no difference.

All in all was well worth for EUR 300.