I agree the Dell XPSs are hit or miss on quality. I had a 9550 and after dealing with its issues moved over to the Thinkpad line (with Linux). Zero problems after that + better a much better keyboard than the Dell. I will say even on Thinkpads you cannot approach the greatness of the Mac trackpad ...

Maybe the 13" XPSs (dev editions) are better - I dont know.

I do think that if you are going Dell @ 15" it may be worth checking out the Precision line. Since this is the business version of the XPS it may have better build quality.