I got a new computer and have had some time to put it through its paces. It's a Dell Studio XPS, with a Core i7 920, 6GB of RAM, and a 24" display. All things considered it was a pretty good deal (ordered in January, $1060 shipped). I later upgraded to 2TB of disk.
This thing is blazing. And building with make -j8 makes me happy inside.
As far as I can tell, everything in it works out of the box with all free software on Ubuntu GNU/Linux Jaunty Jackalope (9.04) x86_64. (Even the ATI Mobility Radeon HD 3450.)
The display, a Dell S2409W, is nothing to sneeze at, either.
There is space inside the case to mount an extra hard drive. It goes in vertically, which is nice because you don't have to wrestle with all the cables and wedge it past the RAM to get it in. However, there is only space for one additional hard drive.
Power consumption is much better than my old desktop. The machine idles at 97W. This goes up to maybe 170W at high load.
My only complaint is the noise. The fans go on like a leafblower when you're pegging the CPU, but I don't really care about that part. The problem for me is more the baseline noise. The computer isn't loud, per se... but it isn't quiet either. It's in my room and I put on earplugs when I go to sleep. Take that with a grain of salt, though, because I'm a person who has trouble falling asleep in the presence of a wall clock.