I run Win98SE on a custom rig.
Athlon 550, Asus K7M, Voodoo3, SBLive! Value, Linksys LNE100TX NIC, ATi TV-Wonder, RealMagic Hollywood Plus, 384MB of Micron PC100 2-2-2 RAM, Pioneer DVD Rom, Yamaha CDRW, IBM 75GXP and a Fujitsu 5400RPM...that's about everything important I think.
The only time I can remember crashing is when I'm messing around with drivers. My system is very stable. Lately I've been turning it off daily because electricity cost in Calgary is suppose to triple in the next month ouch...:|
But for all of september and october I left it on 24/7 and rebooted maybe once every week or two when system resources were very low.
I don't think Win9x is a great OS, but I firmly believe that these people that crash all the time have some messed up configurations and driver conflicts, or they are using cheap low quality parts *cough*abit*cough*