I've had mine done by Monzasport and it does give you a noticable power increase (7to 10% supposedly). Definately worth the money in my opinion. I proabably would have gone to Autodelta as they are more well known, but their prices were about £100 extra at the time compared to Monzasport.
I mostly do town miles so I don't know what the fuel economy is like.
The only problem I've had which I'm not sure is related to the remap is that the idle speed fluctuates when the engine is cold. Having the throttle body cleaned fixed this and I'm putting Redex (Injector cleaner) in the tank now and that seems to help
Kristian (156 2.4JTD 140BHP)
On my 2nd Amazon Green