Hey guys, thought I'd weigh on on this one. I'm more active on the e90post forum but Mark has tuned my '08 335xi coupe to great effect. With his software tune, the best way to describe the increase is to imagine 200 lbs shaved from your car. The acceleration and response is much more quicker, especially in the lower RPM range. The added bonus of the tune has given me better fuel mileage as long as I'm not driving like a maniac.
In terms of dealing with Mark, he's been a class act all the way. When I first had him upgrade my software, I discovered a crack in my intercooler that limited any gains from his tune. He had no problems removing the tune until I got the problem corrected and didn't charge me a penny.
Anyone who'd like to see the tune in person can feel free to PM as I'm in the Toronto area. No error codes have been thrown and he customizes based on any mods you have added (larger intercooler, charge pipe and down pipes for me). Let's step away from the bashing and let the tunes do the talking.