URL bar:

• Clicking an entry in the URL bar autocomplete list should open that page instead of just putting the address in the bar and requiring to press Enter.
• Search by any part of the URL. For example, if I had previously visited http://www.linux.org.ru/view-all.jsp, I expect it to come up when searching for "lin" or "view".
• Better cooperation with faulty themes. The bar shouldn't go all black just because the QtCurve and GTK themes draw gradients incorrectly.

Tabs:

• Close button on each tab (not possible until Qt 4.5?).
• Closing by middle click

Search box:

• Google Suggest dropdown list
• Support for local search engines via OpenSearch (implemented in midori, which uses webkit-gtk)

Bookmarks:

• One-click bookmarking - just add it directly to the menu, or to a subfolder, not to "Uncategorized" like in Firefox 3

General:

• Improved scrolling and textarea typing performance - probably a problem with webkit in general, since the GTK version suffers from this as well
• Ad blocker
• Per-site configuration for enabling JavaScript, plugins and images