One of the best features in a browser I've found in a while was introduced recently in Firefox 5. It's called "App Tabs", and it allows you to pin sites that you always use into your browser so that every time you open it the sites are automatically loaded. It also makes the tab much smaller. So handy for sites I always leave open like Gmail, Facebook, etc.. Read more here and then download here. I also just started to experiment with the Firefox Synch feature, which allows bookmarks and open tabs to be constantly in synch between my desktop, netbook, and my iPhone. Seems to work pretty well so far, so long Xmarks plugin.
Firefox (and other browsers as well) are starting to ramp up their release schedule for new versions. This is great for consumers, but man does it suck as a product manager for a web app when you have to spend half of your life regression testing if you wish to support various browsers.