On a MacBook with a slow hard disk, there is a big difference in startup and shutdown speed between Tiger and Leopard. Graphical errors can be as simple as this:
- Enable Graphite
- Make a Cocoa window inactive
That results in:
Notice the last one... Leopard has many of these small errors and unpolished bits (they are fixed in Snow Leopard though). It's great that Leopard works fine for you and many others I guess, for me, it doesn't. I don't like it, I will move on to Snow Leopard and forget about Leopard as soon as possible.
Edit:
About localization, my primary language is Dutch. But when I insert and empty disc, an English popup will come up telling me I've inserted an empty CD. That's stange because that same window was translated in Dutch in Tiger. Not that I can't read English, it's just stupid. Again, fixed in Snow Leopard.