OSX Snow Leopard on MBP, Mountain Lion on Mac Mini, Win 7 Home Premium on gaming PC, Win 7 Pro on work laptop, Windows 8 & Server 2012 on virtual lab kit.
Mountain Lion has been the most problematic and most of that was having to use Terminal to kill one or two applications but has generally been much better since the MIni was upgraded to 16GB and a couple of open source apps uninstalled.
I used to run OSX Leopard on my old G5 Power Mac and Vista Home Premium 32bit on my old Dell XPS and both were rock solid with only the odd driver issue to solve.
Windows hasn't been a total pile of crap since Millennium Edition. The only BSOD I have had recently have been on the gaming machine when over-clocking and getting the memory settings wrong. Every time I have dealt with a server at work with a Kernel panic or BSOD it has been memory related - either the installation engineer not understanding NUMA ram allocations or dodgy chips (thanks IBM).
As far as mates machines go it has always inevitably been user error that has caused problems - often from going to web sites they shouldn't or from using peer-to-peer networks.