Well in my experience it's been all good. At the end of the day as well, Andrew will happily chat with you about any issues you have whether it be the use of it or the fitting, just give him a shout!
The figures are probably a little optamistic with the DPF in place I'd say. I think it's something like 280bhp and 660Nm but I don't think you'd be getting that to be honest. I'd say that about 260bhp and 600-620Nm is a better guess. Regardless it's enough that you'll notice it both in the outright speed and economy. The extra power has to come from somewhere so provided you don't expect high economy while flooring it everywhere you'll be fine.
I fitted mine with 600 or 700 miles showing on the clock because I got impatient but there haven't been any issues because I'm conscious to let the car warm up and cool down. The only issue I had was when I turned the box up too high and punched it which made the EML come on. There is no error recorded though and by turning the box down a notch and turning the car on and off it's gone and just lets you know the limit of the tuning.
As for fitting, it really was a 5-10 minute job provided you don't have huge hands. Two plugs to undo and then find somewhere for the box to sit. Done.
Hope that helps.
Oh and a good choice of car btw.