my dell 6000 (pentium M 730) says the battery life is about 5 and 1/2 hours. I've never tested it though.
For me it was always speed and hard drive space in a desktop vs cost of a laptop. When I built my last desktop about 2-1/2 years ago I put almost the top of the line everything in it and came in under $800. At that time a comparable laptop was not really available with the HD and RAM that I wanted, and the cost of high-end laptops was at least 3-4x higher. Now like you eluded to, the cost has come way down and the power has gone up.
I got the laptop a couple of months ago mainly so my wife would have a computer to use and I could keep working on my desktop. I originally considered maybe using it for my work but when I tried to run dreamweaver and photoshop together it was really slow. Then I read somewhere that by default the laptops power setting might be slowing down the computer to save power even though it was plugged into AC. When I swithced the power setting to the full power setting the computer really seemed to speed up. I don't know if I just imagined it or if it really is faster.
Now I am considering moving everything over to the laptop as long as I can use my 17" LCD and mouse and keyboard (no PS2 ports though.)
Dell doesn't make a proper docking station for this model but they do have a port replicator that I think has PS2 ports. Anyone ever use on of these things? Do they work pretty well?
It would be nice to get out of the house every once in a while and go work at the beach or something. It's kinda hard to do that with the desktop ;-)