Slowaris is crap. SunOS was much much better. And then there is the whole issue with Sun machines being generally underpowered. It takes them years to fix fundamental flaws in the OS and they deny critical misdesigns in the hardware which have led to significant reliability issues.
The only reason sun is even around today is because HP so totally mismanaged the Apollo transition that sun was able to gain significant market share. Sun has been living off that market share ever since.
