i'm sorry to hear you had such problems with the o350. as jan-jaap i got mine rather late in 2010 after and because of my forced time out but never had it on around the clock. yet i didn't have problems either and that despite my rather humble customization due to the differently sized 1ghz module.
i ran an o2 for a few years as a server which was fine as well. only after turning it on again several years later i had to re-seat the rams once. fine again since.
as for the fool i can't say anything because i never had one.
only last fall after exactly 20 years of flawless service my extreme gfx bit it and that was the first and only issue i ever had with it. put in another one (thanks to ian) and fine again.
my octanes have been rock solid just as everything that reads ip27 somewhere so all in all at least for the machines i had and knew of i can say reliability has never been an issue.
same goes for my alpha btw. pulled it out of storage a few months ago and fired it up. although it's "only" one of the pc164 models it just worked.
regarding x86 my experiences however were very different. reliability? not by a longshot and tons of "never to be solved" mysteries i gave up on investigating at some point. non-existant hardware diags add to it. since i started running osx there around 2007 a couple of machines just died and i had some of the mentioned mysterious issues along the way. it even fried a monitor once thanks to some crappy gfx drivers and/or card. another example sometimes when i turn it on the network is down; i pull the cable, stuck it back in and then it's fine ... you get the idea, stuff that doesn't fuel (pun intended
) trust much. not to mention the crappy hfs but that's not the hardware's fault so ...