I've just bought one, had it for about 3 weeks now. It's had quite a bit done to it including a remap. I only bought it because my Q7 was making some funky noises and I was worried it was going to let go in a big way.
This one is running 350bhp and 700nm of torque. With all the trinkets on it (some pretty tasteless ones!) and 58k miles I paid £16k. Black with black heated leather, sat nav and so on.
Pro's - it's bloody quick. In all fairness if it could get the power down (see con) it would be close call between this and the RS4 I had. Overtaking power is daft and cruising speeds can be silly if you don't keep an eye on things. I honestly don't think you need the map, I had a go in a standard one and it was plenty fast enough. Also, if you don't buy a barried up one like mine nobody really knows what it is. I had a porsche and EVERYONE wants to race you when you have one of those. The irony is this is much quicker but nobody cares - its debadged so people think its just some chav 318.
Con's - I think in part its to do with the tyres/wheels (tyres on the back are 285/25/20) but its BLOODY bumpy. I've had an Msport car before so knew what to expect but this is on another level. Also, it really does struggle to get all the power down. The traction control light is constantly flashing in the first three gears and I had it break traction at speed on the m25 the other night. In the dry I'm sure it'll be much better but it really does need a proper diff in it.
Fuel wise I'm getting roughly 33mpg. I've had 40mpg on a run sat at 60mph but I felt like killing myself at the end of it.
I also should have bought an estate - I've put a rack on this now but its not ideal. And whistles for England.
Overall I like it. It's proper quick yet not (quite) as bad as the quick cars I've had on fuel. Seats four (at a push) and looks ok. Not sure I could have a 330d as I'd always wish I'd got the 335....IMO!