I personally find very few bugs, if any, in OS updates these days.
....True about less bugs but it's surprising how many third-party developers take such a long time to catch up, especially with plug-ins for Logic Pro (Waves, for example). I tend to follow the advice of very experienced professionals who don't move up the Mac OS ladder until very late in the cycle. It depends what you use your Macs for.
I think that Lion only reached 10.4 but Snow Leopard, great is it is, reached 10.8.
Also, as I regularly move Logic song projects to and from home studio to a close friend's pro studio, our Mac OS's need to match. I'm not advising that everyone should do as I do but only that it's wise not to jump in on any dot zero version of any software. I even waited a month before updating my iPad iOS.
Reading about Mountain Lion it seems to concentrate more on how it drives consumer Apps rather than professional Apps.