I'm running 3.0 GENERIC.MP on a Sparcstation 20 with 160 MB of RAM.  Uptime 
right now is 24 days 13 hours so obviously things are stable.  I'm not 
running X though - I'm just running the system headlessly.

I have dual 50 MHz processors.  I've upgraded the RAM a couple of times 
myself.  I also installed an SBus "Happy Meal" 100BaseTX Ethernet card a few 
weeks ago.

I've noticed that my particular machine is a little snarky.  I don't think 
the CPU cards were making really solid contact with the sockets.  I got a 
couple of new 70 MHz processors for the machine and installed them along 
with my RAM upgrades and found out that my boot PROM was too outdated to 
permit the new processors, so I put the old ones back in.  Ever since, the 
machine has run extremely well.  Perhaps I wore off some corrosion in the 
sockets or on the CPU card pins.

In any event, it's working very well now so that points to NetBSD 3.0 being 
stable on this platform.

Jim