A few Leopard observations
Still getting used to Leopard, which continues to impress. A few observations, mostly visual.
Spaces
It’s curious that tiny representations of the individual spaces are not displayed on the overlay when you invoke Spaces. They were likely considered, but if so, why weren’t they adopted? They’re not as clean-looking as the flat white that was used, but they provide additional and useful information.
[Leopard's Spaces is on the left. An altered version with representation is on the right.]

Placing Mail Activity in the bottom of the sidebar seems great, but that pane looks rushed. Why is it lighter in the middle, for instance?

And why is the text “MAIL ACTIVITY” lighter as well? Perhaps to convey its different nature, but it’s too close in value to “SMART MAILBOXES” and the other section labels.

Finder
The question mark to the right of the search field in Finder windows is nicely done.

The confusion between Desktop icons in the sidebar and the window titlebar is not.

Safari
The elegance of Safari’s Find was already evident in the beta, but the final version is better still. The border around the current find selection is thinner, making it easier to see the context on either side.

And note how easy it is to see which passage is currently selected: round corner vs. square, colored background (with a gradient, yet) vs. white, broad padding around the match vs. narrow, and drop-shadowed vs. no drop shadow. Those four differences combined keep it clear where the selection is, even on busy pages with many matches.

iChat
Chats are archived one level deeper than previous versions, in a folder for that day:
~/Documents/iChat/Ed Asner on 2007-10-30 at 20.03Leopard:
~/Documents/iChat/2007-10-30/Ed Asner on 2007-10-30 at 20.03
Interesting observations. However, regarding window vs. sidebar icons, there is really no confusion. The window icon associated with the name of the window represents the folder ONLY (being a visual cue for the folder), whereas the icon in the sidebar represents the desktop, which is a broader concept than just the the desktop folder alone. They should be different!
Er, that question mark looks an awful lot like the “missing icon” indicator that has been in previous systems. In any case, there’s no question mark next to my Finder’s search bar in Leopard.
Issa, you’re right. That question mark is a separate toolbar item, apparently broken in Leopard. Maybe it was something already there in Tiger that broke during the upgrade, but I don’t think so.
It actually worked well with the search field in that position.
The new Alex voice in Leopard is pretty good, too.