I haven't had the time to explore Leopard yet. All I know is I hate what they've done with the interface.
Yep, 's about the only gripe I do have. I've already hacked it to disable the glass shelf dock (Apple put a plain black transparent dock in it for the left and right side, and you can switch the bottom one to this via a command at the terminal

). The semi-transparent menu bar is irritating as hell too, I hope someone finds a hack for that too.
Overall however I'm truly impressed by it. I was a bit down after upgrading from Panther (10.3) to Tiger (10.4) because I didn't think Tiger offered enough extra stuff that I found useful. Going from Tiger to Leopard (10.5) feels much more like the kind of leap you should make when you move to a major new version. I already can't live without Spaces, and Time Machine makes me feel like my data is at least somewhat safer

Like I said - AInc would need a genuine Miracle to beat this kind of OS.