Fair to say 3.5 had some serious performance issues when released
Most if not all tried and proven solutions to the browsers problems can be found here
http://kb.mozillazine.org/Knowledge_Base
I dont think running a huge number of extensions is as much of a risk as downloading seperate programs from individual software developers would normally be because its under the firefox
umbrella but it does increase the chance of conflict & puts more burden on your computer
Less is always more and judging by the 5000+ extensions available,
I do wonder why they dont cull a lot of them as many overlap or do exactly the same thing
which makes choosing a bit of a nightmare at times
One site I found had tried to pick extensins from the point of view
what do you want to do/see.....maybe useful...a to z format
http://www.econsultant.com/i-want-firefox-extension/
Heres a novel one but a very useful one all the same
ColorfulTabs is an add-on for the popular browser Firefox. Firefox is known for its tabbed-browsing feature(s). ColorfulTabs takes the experience to the next level. ColorfulTabs colors every tab in a unique color and makes them easy to distinguish while enhancing the appeal of the Firefox interface.ColorfulTabs is the favorite of the Firefox users. In the words of one of the million users…
ColorfulTabs 4.1
by Shivanand Sharma
http://www.binaryturf.com/free-softw...s-for-firefox/
comments from users
https://addons.mozilla.org/en-US/firefox/addon/1368