I had a desktop Zeon system in my last computer. I actaully had a $8,000 system and it quite plainly kicked ass!!!
Dual Zeon (P4 format), 2 gigs of memory, Ultra320 SCSI RAID 0 and an Oxygen OpenGL something (I forgot the model but the video card was $3,200 by itself). This system kicked ass. I don't think I needed a system that powerful, but they had a the same system for all modeling and analysis by design. I used it to model and design testing fixtures for our porducts.
This computer actually showed up as 4 logical processors in my Windows XP Pro.
Bottom line...yes, you can use them as a home computer just the same as you would any other computer.
BTW...HT (Hyper-Thread) is two logical processors in one physical CPU. I love and use mine all the time. I can ALT-TAB bewteen windows programs and games (i.e. Counter-Strike and UT2004) without seeing any loss of performance at all.
Soyo Dragon Ultra Platinum Edition powered by a P4 3.06GHz w/HT @ 533FSB
ATI Radeon X800Pro 256DDR <---Yeah!!! I finally got it!!!
1024MB PC3200, Creative Audigy LS, 2 x 40GB = 80GB RAID 0
Windows XP Pro, DOOM 3, CS, UT2004, BF1942 RtoR, CNC Generals
Finished Half-Life 2!!!!!!!!!!