I have made the mistake on previous releases of Mac OS X, other operating systems, and even software applications of upgrading immediately on a "dot zero" (.0) release, something I typically advise others to avoid. However, the pain I suffer is mitigated by helping others, and as a tech writer, it's sort of my job to be on the bleeding edge to file reports back to later adopters.
Leopard is an interesting case. I had used Leopard betas, and updated a test Power Mac in my office - one that I will be selling one of these days - to the shipping version of Leopard on the day before its formal release. A few days later, I installed 10.5.0 on my home PowerBook G4, suffering problems I've documented elsewhere due to an out-of-date copy of PGP (see "PGP Causes Leopard Slowdown, But Fix Is Simple," 2007-11-13).
However, my regular work machine - a Mac Pro I bought in spring - remains on Tiger. And what I'm finding is that as every day goes by, I'm looking more and more for missing features in Tiger that I use at home in Leopard. Even with the 10.5.1 update, I still think Leopard has a bit to go in fixing some security design errors and in a few areas of stability and functionality.
But I find myself on my Mac Pro looking for Quick Look, a functional Spotlight (instead of the okay but not great one in Tiger), Back to My Mac (once I got that working), and even some of the glitz like Cover Flow in the Finder.
I'm not ready to take the plunge yet: I need to be sure of 100-percent functionality for my daily work. But I'm strangely close to making the move. Maybe with 10.5.2, whenever that comes, I'll finally be ready.