I have built five systems using ME with an Abit BE6-II mobo, PIII 533, and 128 megs of ram.  These have all been very stable with few problems.  I did have problems with modems but I switched to 3Com and these went away.  On OEM systems I have found if you shutdown some of the extras that are loaded at start-up will help with lock-ups as well.  For me HP scanner software causes more than its fair share of lock-ups.