I travel a lot, and schlep my laptop around a lot when I'm at home. My 15" is a bit too big and heavy, but I do it anyway. My four-pound Sharp was perfect, except the screen resolution was too low to be useful.
A 17" machine wouldn't fit into my camera backpack.
Besides, a 17" screen is just too big. I like lots of data compressed into tight visual spaces.
The 3g modems that Dell has built into the mobo's of the laptop's are pretty sweet. I see you're not ordering one. You just slip in a sim card from a provider (like AT&T) and there's no external antenna anywhere, and you've got everywhere connectivity.
If you're the kind of person that would want to work at the library, or starbucks, or if you travel much and hate how hotels rape you for poor internet access, or if you spend a non-trivial amount of time in places other than your desk, it might be worth it.
I can't really claim cost/benefit since my workplace pays for it.
You can accomplish the same effect by buying the PCMCIA or PC-Express pluggable modem, but its a dongle that sticks out the side of your laptop, which can be aggravating.
I just got a new laptop at work and since I didn't configure the new one, it didn't have the 3g modem and I have to confess, it's made me sad. When I'm on travel I can't just whip it out and connect anywhere.
My AT&T service runs about $80 / mo, btw.
Oh, and it's 3g, so you can use it in a moving vehicle or train because the protocol has a handoff from cell to cell, unlike wifi.
I like the dell fingerprint readers, but at best they stop you from logging in.
A motivated thief like me would just pull the drive out of the laptop to get what I wanted and bypass the reader if you didn't tie the reader to some sort of encryption software, which is hard with the Dell laptops.
Do like I do and install pgp for windows and put all of your stuff on a secure virtual drive. Then when someone wants to get it, it becomes either an intimidation or a Fourth Amendment issue.
Intel integrated graphics cards are pretty minimal. And the more graphic card RAM you have, the happier Photoshop will be.
Adobe is currently shipping version 9 of Acrobat Standard.
I'd aim for a Dual Layer DVD writer drive, if possible.
With the data density of the 320GB+ 2.5" drives, 7200RPM isn't quite as necessary in a good laptop as it used to be.
Glad you're getting an XP downgrade, Vista works, but it doesn't make me happy. (Well, Windows doesn't make me happy at all, but XP is a more known and less irritating lack of happiness than Vista is at the moment.)
If you want faster Bluetooth, get it. There is no too fast.
If it has IEEE-1394 (FireWire) as an option, that's faster for Photoshop levels of throughput for hard drives than USB2 is. 1394B is faster yet (FireWire 800), and fastest is eSATA. These days, I'd aim for eSATA. (And I'm buying and speccing all external drives with eSATA for future compatibility.)
I still think you're a loon over the screen resolution, but my eyes suck so that could just be personal bias. :)