Speed is the reason many people choose it, not necessarily a priority for me. I prefer reliability and features over speed myself (unless speed *is* the feature needed). Solaris is fine on reliability, but a bit weak on features I care about (like Infinipath support).
As for proven vendors, Redhat is perfectly adequate and I've never seen a RHEL 4.x box crash. Many RHEL servers have uptimes of years. Heck, we had a mid-sized database server that ran for almost 3 years under 24x7 load on Redhat 9(!) before finally taking it down to upgrade to RHEL 4.x. This kind of reliability is the norm.
Funny you would leave out the monsterous detail that was a forced upgrade, after RH dumped all support for RH9 completely out of the blue and left their customers like you completely stranded. Apparently you ran for a long while without paches too which tells me all I need to know about your admin ability, or lack thereof.
Wow! 9 was not their best work.. 7.2, and 8 where the most stable pre rehel releases..