I'm going to chime in as well that the Via chipset is a blocker for me on the D900.
Nforce 4/5 (there is no mobile version of the Nforce afaik, thus this is a wish list of course)
7800go (would take 6800 go ultra if I could count on true upgradability - ie faith) A promise from a vendor would go a long way here...but truly the makers of the chips need to live up to the promise too. I all too well look back at the XPS Gen1 and ask "where are the upgrades to its graphics card? Where is the 6800 go ultra for that?"
Ability to use a second battery instead of a second optical or hardrive. Be nice if I could use either a 2nd HD or a 2nd battery. Can see occasions where one or the other would be very useful
4gb of ram (M2 and DDR2 would be quite a plus for long term ownership) 2 is good, mind you, but the top end which can fully use 2gb now, is going to be happier with 4 in 18 months, which is when most laptops start getting far behind the curve
Creative sound chip. Azalia is nice. But mobo makers and maybe Creative as well are smartening up to the idea that instead of AC97, it would be quite a coup to manage to have a 2zs or even better the xifi internal to a mobo or notebook
Spare parts. Would be nice if we had the option of buying a couple of extra keyboards (the really do wear out) so that a year down the road we could just switch out ourselves.
E-SATA. When on earth are laptop makers gonna get the clue that a full SATA speed bus for an external drive would be a godsend to mobile users? Imagine being able to use (at the office or home) that super high speed raptor drive, or the 500gb drive on a bus that is just as fast as if the drive were internal? SATA 2 or E-SATA, you could take your pick but it would be really useful, and seems to me not much harder than a USB plug to build into a machine.
Anyway since the Nvidia chipset is the vast preference here, I fear I'll either have to wait for such a machine to be built or look hard at the Yonah based machines (which won't honestly be the equal of the X2, sigh) when they arrive.
imo, its wise to consider 64bit for the several year haul, as I think it's rather telling that Microsoft internally is buying AMD based servers. When the coders actually catch up to the hardware it isn't going to be night and day, but as a machine gets older you'll want every ounce of speed you can get out of it. That means picture how fast this laptop will be in 2 years, and realizing you might even be able to coax 10% more speed out of it using 64bit software and I think you'll see the value.
X2's and the newer AMD cores are power misers as well. I'm rather surprised that the D900 only may get 1hour of life. I'd expect that they would do better, specifically if a P-M gets about 2-2.5 hrs and a P4 9880 gets 1 hour I would have expected the D900 to land in the 1.5-1.75 range, maybe a bit more if you used it lightly (non-gaming). Get 2 extra batteries (I'm big on having spares around) and you'd have a medium plane flight or plenty for a presentation, let alone a good long intense gaming session.