For instance (in 9.0.597):
* Mouse over a tab, and move your cursor back and forth. The whole tab is highlighted, but there's extra brightness around the cursor.
* Similarly, look carefully at the buttons on the main bar, or at bookmarks, when mousing over. There's a subtle brightening over a fraction of a second, instead of an instant-on hover effect. Don't believe it? Compare it to mousing over the "+" new tab button, which is instantly highlighted to its full degree.
* Tabs, when re-arranged, slide to their new positions instead of snapping.
* URLs lose http://, and everything after the first "/" is very slightly grayed instead of black.
* Every corner is curved. Every dark edge is under-highlighted, so tabs seem to "float above" the rest of the UI. Those back / reload buttons seem to be recessed black icons instead of buttons - until you mouse over them.
* "Active" chrome elements - active tab, browser + extensions, and bookmarks - have a light -> dark -> light transition through all of them. Inactive tabs are noticeably closer to a solid, darker gray, though they to have a slight gradient. It helps unify the active tab with the applicable chrome seamlessly. You'll also notice Firefox 4 has adopted similar visual cues for tabs.
All of which adds more visual cues to what things do, and easier hierarchical organization at a glance, while maintaining extremely minimal clutter.
There are also a couple things I dislike. Like how utterly massive the bookmarks-in-folders on the bookmarks bar are. Almost twice what other browsers have / via the menu. Glitches in Web Inspector. Excessively-useful hidden preferences. But overall, there's a frightening amount of polish in Chrome.