I got the XPS 2 notebook last year because the m7700 was too heavy for me (already had an AW desktop), and the AW 15" model had been discontinued. The Dell has performed flawlessly, and is light enough to use on my lap and carry with me occaisionally. BUT - I'm looking to get the m5500, because I really do want a smaller notebook.
Other companies sell the same basic computer as the m5500, but I much prefer the Alienware model for these reasons:
1) I like the styling
2) Even if I have a problem, I know you can eventually get through to a real person who will make sure you get some help (this, from experience with the Aurora 7500)
3) The regulars here at NBF Alienware are a big help and an interesting lot
I will continue to monitor other brands, but will only stray from AW if I find a lighter, more powerful 15" notebook...(and these factors would need to be a significant improvement). I'd also prefer an AMD-based notebook, but experience with the Pent-M tells me it does all I need.