Opera's default interface is too cluttered. I happen to like using 800x600 windows so I can see what's going on in other apps as I work. Do you know how little space that leaves for Opera for showing Web pages? zOMG forced horizontal scrolling.

Even after spending time cleaning up the interface and ditching all the bookmarks and toolbars, I'm constantly reminded that there's something I'd like to do that isn't being done.

Why can't the Transfer window automatically delete all completed downloads from its history?
Why can't a view the source code of only a selected part of a page?
Why can't I write my own custom search engine shortcuts for the URL bar?
Why does it not cache images that have been scrolled offscreen but are still on the same page (they're rerendered each time I scroll them back on screen)?
Why can't I do a right-click Show Image on images that failed to download without refreshing the whole page?
Why am I forced to arrange my bookmarks in alphabetical order?
Why can't I use UTF-8 characters in my bookmark titles?
Why can't I use native Qt widgets with "native" skins? Come on, even Firefox, a GTK lookalike, does a better job!
Why can't I select certain font sizes? I want 11px fonts to be consistent with the rest of my apps.

Firefox does it all and does it well. Anything it doesn't do, I can make it do with Extensions. What's not to like?