Ok I just bought it literally 30 minutes ago.
I have been pondering this for honestly hours upon hours over the past few days, the cons and the pros. First off, Dell will undoubtedly be releasing the XPS M1710 in a matter of days. It will have a better chipset in the 945PM, which allows faster memory at 667mhz aswell as a maximum of 4GB. It will have a core duo processor along with either a 7900GS or 7900GTX go, with the 7900GTX providing about 15% better performance aswell as a more advanced architecture with 90nm as opposed to 110nm with the 7800GTX. In short the new XPS M1710 will be better. But then you have to factor in cost, aswell as the arrival of Windows Vista in January 2007.
When Vista hits, it will hit with Intel Merom and DX10 capable graphics cards, no question. BY the time Vista has settled in, which is about 12 months from now, there will be a new and improved XPS by then, which is more suitable than the upcoming XPSM1710. The new XPS will cost substantially more than they are selling the M170 for now I think, and it's worth saving perhaps $1000-1500 on the new XPS and put that towards a future vista notebook next year, as the current XPS is more than capable up until and perhaps through the beginning of Vista.
Conclusion, if you want the best of the best creme de la creme, wait a few days and get the XPSM1710. If you can settle for something very good but not quite the best, but at a bargain price, get the XPS now and put the difference towards a Vista based notebook next year. Sorry for the long post, just went through the possibilities.