I've only built one machine myself, but I've been inside any number of machines starting with a DEC KI-10, numerous unix boxes of the '80's (mostly MC68000 based), SPARCstations, various PC's, etc. The only one I really sliced myself on was a VAX 11-780; I was trying to get at the Unibus and nearly took off a finger. Most of the hardware engineers I worked with had a nice scar collection.