I've always built my own PCs, but after seeing the newest Alienware in Computer Gaming World, I fell in love with it. If I could somehow get the case, I'd probably just build one myself again.
One thing though, I configured a Athlon XP 1800+ system with an Asus A7N266-C motherboard, 256 megs of RAM, 40 gig harddrive, Visiontek Xtasy GeForce4 MX440 video card, Sound Blaster Audigy 5.1 w/1394, a NIC, Keyboard, and 1 year of tech support for about $1,200 with free shipping. That's not too bad, but you could definitely build a similar PC for a couple hundred dollars less. But it wouldn't look as cool...