Got the machine that I ordered for my longhorn, etc. experiments. I actually got it on Friday, but my wife told me in no uncertain terms that I needed to finish my latest article for the MSDN ASP.NET Developer Center before I opened the box. She was right, of course, as I proceeded to (as soon as the article was done and wending its way to Kent) stay up until 5am getting the server (mostly) set up.
In addition to the stock setup that I ordered, I added 1GB of 400mhz DDR RAM, an inexpensive Radeon 9200se knock-off (8x AGP, 128MB video RAM), and a 4X DVD+R/RW drive. I didn't have a chance to install the software for DVD playing/burning until today, but the only problem I ran into was that the freebie version of Roxio's Easy CD Creator (with DVD) stinks, big time. It's an old version, of course, and although I was able to get it to recognize my drive after downloading the latest patches, it locked up at the very end of the burning process, and required a reboot to unlock the drive. So I downloaded a demo copy of Nero, which seems to do the job much better. Perhaps worth the $70, if it'll save me from destroying disks left and right (and pulling my hair out).
The really excellent news is that I'm able to confirm that all of the 800mhz bus versions of the 400sc use Hyperthreaded processors. Since the first OS I installed was Windows Server 2003 (I haven't gotten around to installing Longhorn yet, probably tomorrow), I didn't need to do a thing to enable hyperthreading. So far, the box seems very zippy. We'll see how the performance is with Longhorn.
To make a long story short, whether you're looking for a machine to play with Longhorn on, or just an inexpensive server or workstation machine, I would certainly recommend that you take a look at the Dell 400sc. It's inexpensive, the performance so far seems very good, and the build quality and attention to detail are really impressive. The chassis is nearly completely toolless (the only exception being that you need a screwdriver to attach the drive rails if you're installing a new drive), and is set up to make upgrades almost entirely painless. To upgrade the video card I simply opened the case, released the latch holding in all the expansion cards, removed the crappy 8MB PCI card, installed the new AGP card (note that AGP is functional, but not officially supported), and replaced the latch. All of the drive cable plugs have loop handles so that you can remove the plugs without straining the cable or bending pins...very well-thought out. As if you can't tell, I'm very pleased with this machine (I'm already considering buying another to replace a noisy rack server I use for my Web server...unlike my noisy box, the 400sc is nearly silent).
UPDATE: If you're running Longhorn on hardware (as opposed to in a VM), I'd be very interested in hearing what kind of video card you're running and whether you have hardware acceleration working properly with the card. If I can find out about a card that's verified to work with Longhorn without crashing it, I may bite the bullet and pick up a new card to see what difference hardware acceleration makes.