Nothing in the concept of FLOSS promises floss software to actually be more high quality or more stable. All it guarantees is that you can distribute it and modify. So why would it magically be more stable than proprietary?
No, I get you're serious - more amused by how different your experience is to my own - I'm sure I can crash a Mac by looking at them. ;-) I'm not necessarily saying that there aren't problems, but that it's far less likely in my experience that a FLOSS system that's working solidly one day will behave differently the next.
But actually there is something in FLOSS that I think does sometimes make for more stable software, if less featured - there's no money to be made in fixing bugs.
Mind you, my usual response to anyone asking me why I work with FLOSS is that I got fed up of paying for software that doesn't work properly - we've got all our own shit that doesn't work properly, but at least I don't feel like I've been screwed over. ;-)
Best wishes,
Neil