Add-Ons are Great, BUT...
I think there are tons of add-ons out there that can make life easier. But just remember, add-ons can become very addictive and if you are not careful, before you know it you will be using 5-10- maybe 15 add-ons in no time. This will substantially slow down your browser.
So be careful what you choose, be picky.
Think of it as a runner having to carry an additionally rock on his back each time you install another add-on. It will slow him down.