Firefox really starts to annoy with it’s frequent updates, but still I use it. Bellow are link to add-ons which I use and maybe you should try:
1. AdBlock Plus – this is the first add-on to install every time. It’s purpose is to block advertisement, but you also can block content you do not want.
2. CoolPreviews – simple addon, which let’s you see link only by hovering mouse over icon next to link in a small preview.
3. Download Statusbar – replaces download windows, with a bar, which shows ONLY when you are downloading something, it appears at bottom of Firefox windows. I like this one really much, because when you download lots of files, window of download comes to front every time.
4. FireGesture – add-on which bring mouse gestures, you can simply draw line to move forward or back pages, there are more commands.
5. Status-4-Ever – add-on which add loading progress in address bar. Not really necessary, but nice to have.
6. Stylish – restyle ANY web page, you can install styles from internet, or write your own.
7. Tab Scope – add-on which add mouse over tab function, which shows page.
8. TinEye – rarely used, but when used it does it’s job. It allows to find image, mostly bigger image of one you find on internet.
9. YouTube video quality manager – simply set video quality you would like to use, and it will by set automatically.