As a rule, when there is a software version X.Y.Z for anything, I usually wait for Z to be at least a 2. I don't need to be on the bleeding edge, but it's nice to be fairly current when possible. I was running a Mac PowerBook G3 (FireWire, Pismo, 2000 model) on MacOS 9.2.2 until about 2006 when I got a MacBook.
I love my vintage Macs, especially the PowerBook Duo (1992) and Duo Dock.
I am gingerly approaching the possibility of upgrading from 10.6.8 to Mavericks, having upgraded the RAM to 8 GB and internal boot drive to 1 TB, 7200 RPM, and MS Office: Mac from 2004 to 2011 on my Mid-2009 MacBook Pro.