First up is Mozilla's directory of addons. Useful as they may be, these sites are still clunky as you have to always have to adjust what you're searching for - even when you're already browsing a specific section. Further, with the mountain of extensions and themes piling up, there really needs to be a way of limiting what addons you see to the version of Firefox you're using. Before I found Foxmarks, I was browsing the addons directory for a bookmark synchronizing extension, and Bookmark Synchronizer kept appearing in the results, even though it only works with Firefox 1.0. While this frustrates me, I'm sure it's even more confusing for all those users out there who can barely tell the difference between Firefox and Internet Explorer.
Next on the list is Firefox's lack of OS X-ability. While Windows XP is lagging behind with barely 20th century technology (hence the need for things like Firefox's password management), OS X already has a bunch of goodies baked in - like the Keychain and universal spell checking - that Firefox really needs to take advantage of. Virtually all other OS X apps place application and web passwords in OS X's Keychain, a centralized resource the whole OS can use. One merely needs to copy the keychain database file (and know its password, of course) in order to back up a record of all the passwords they need to remember. Throw in .Mac service which can effortlessly sync your Keychain (amongst other things) with multiple Macs and you'll be on the next level of synchronization heaven. Let's also not forget OS X's built in, universal spell checking engine which offers a simple keyboard shortcut for a pop-up definition window. In other browsers like Safari, OmniWeb and even Camino, there are no plugins or extensions needed to gain any of these essential 21st century computing features.
So please, Mozilla, answer the call of us Firefox fans who are hoping for a more OS X-ified and more powerful version of your most fantastic of browsers. Mac users everywhere will thank you, and I bet we'd even buy a few tshirts too.