Things important to me:
1. All security patches updated for browser.
2. A Working fast browser
Not important to me. (or things that don't work for me) :
1. Bloating of software with new features - none of them i would use.
(I actually cant remember any major feature given by Firefox that adds to my productivity - its same browser capabilities that i need)
2. Continuous bloating of the software when running in memory. as of now firefox when used with 1 new tab still uses 150mb of active paged memory.
Other day i found solution to this.
Firefox ESR. [Extended Support Release]
Firefox maintains multiple release channels - Beta update, Release channel and this is one another channel ESR. This channel receives security updates and nothing else for 9 iterations of Firefox release channel updates.
eg. Firefox 17.0 will continue with series 17.0.1(includes security updates in Firefox 18) and .2(includes security updates in Firefox 19) and so on with finally upgrading to Firefox 24.0.2(which would be equivalent to Firefox 26 security updates). Now this numbering can change if there are out of turn important fixes but still these won't be botheration as you can choose when to install and these security updates i have seen to be in Kilobytes at max.
Link to download Firefox ESR in your language/platform here.
You would be surprised to see that this is part of Firefox charter to not offer this release channel directly from there home pages. see last point in here :)
Let me know if this helps or you have found other solutions to this.
