Firefox on Mac takes a lot of flak for being ugly and/or slow, but it’s still my primary browser, simply because it offers so much functionality absent from other Mac browsers like Safari. An incomprehensive list:
Incremental find, also known as “Find as you type.” As far as I’m concerned, this is how text search was meant to be: fast, efficient, and unobtrusive. Use this for any extended amount of time, and you’ll wonder how you ever put up with dialog boxes.
Bookmark keywords. Coupled with Quicksilver, this feature allows me to access any bookmarked page from anywhere in the system in less than a second. No exaggeration.
Smart keywords. An extension of the bookmark keywords feature that allows you to access any search form by typing a keyword followed by your query into the URL bar (eg. to search Google for “numa numa,” you could type “g numa numa”). I prefer this over a dedicated search box, which can only handle one search engine (in the case of Safari), or requires you to switch between multiple engines through a dropdown (in the case of Firefox).
Draggable tabs. A relatively minor feature, but necessary for anyone with organizational OCD. Not being able to reorder my tabs after opening them just doesn’t cut it anymore.
FireBug extension. Lightyears ahead of Firefox’s built-in DOM Inspector, and an absolutely essential part of any web developer’s toolbox.
Web Developer extension. Contains pretty much every single tool a web developer could ask for. Another essential.
Greasemonkey extension. Greasemonkey is like Superman; it can do almost anything.
The thing is, I like Safari. I want to use Safari. It’s fast, elegant, and better integrated with OS X. But as it is, it’s missing too many features I can’t do without. Luckily, Apple seems to have caught on, and has implemented quite a few items on my wishlist in Safari for Leopard. Among them:
Incremental find. Safari’s incremental find is even better than Firefox’s, with all instances of the search term being outlined at once, and the rest of the page being dimmed to make them even easier to spot.
Draggable tabs. Again, Safari’s implementation is clearly superior. While Firefox only allows the dragging of tabs within the same window, Safari allows them to be dragged between separate windows. Tabs can also be dragged out to form their own windows (with a nifty transition, no less), and vice versa.
Web Inspector. A very nice-looking DOM inspector, indeed.
Creammonkey. While not actually an Apple-implemented feature, Creammonkey is a Safari plugin that offers equivalent functionality to Greasemonkey.
Despite these improvements, Firefox still trounces (and will likely continue to trounce) Safari in terms of sheer extensibility. But what Safari lacks in not having a large library of available extensions, it makes up for in the elegant design of the features it does implement. That said, if I can get 90% of the features I care about in Safari without spending money on a third-party plugin like Saft, I’ll consider switching. Until then, I’m sticking with Firefox.