* I hope they don't copy iTunes, with its extremely slow interface, lack of features, lack of extensibility, lack of options... etc...
* No tabs: They must use tabs in some confused and different way than me. Generally I have one window per browsing task, e.g. one for Gmail, another for HN with tabs of articles and comment pages I'm reading, etc... ironically it was much easier to work with 10+ tabs before the changes of Firefox 3 where they would scroll off the screen because of their fairly large minimum width... Maybe if people are using one window only, and trying to keep their mail, social networking, online radio, and everything else under the sun open all day, they might get confused, but this is sort of a solved problem. Just open another window.
* Taskfox/Ubiquity: umm, what? Most searches I do in Firefox go right to the built in search box with a simple Ctrl+K, couldn't be easier. I have over the years, starting in Firefox 2, added a few keyword searches to the location bar, because I don't like changing the search box. I have w for wikipedia, and so on. This seems similar, but I'm not sure of the utility of opening Wikipedia in a tiny dropdown... how is that faster, easier to read, or any other good quality? It seems like some kind of half hearted attempt at taking an autocompleting command line and adding some that useful on the web, but I don't see anything... useful.
* Possibly unrelated gripe: I took a while to "upgrade" to Firefox 3 from v2 because I didn't like the "AwesomeBar" and a couple of other interface changes. While I am mostly used to it now, I still can't reliably get the AwesomeBar to autocomplete some URLs. It seems to fixate on the first match, often not displaying the second match until I actually type the full URL, if at all. Not to mention the fact that even when it works, its not as fast as the Firefox 2 behavior of naively autocompleting visited URLs. I don't need to autocomplete my bookmarks, that's why they are bookmarks! I click on them!
I like Firefox, I have since Phoenix 0.4 or so, but I really don't know what they're doing anymore...