All versions are pretty much alike. I stick to 3.6.24 ( I guess it was updated to parallel 8.0). I am using each version with a different profile, in particular different bookmark selections, but discard any old version, when my Desktop is getting too cluttered.
UserAgent: Mozilla/5.0 (Windows NT 5.1; rv:8.0) Gecko/20100101 Firefox/8.0
A minority may be right, and a majority is always wrong
~ Henrik Ibsen
WinXP, SP3, 512 MB, SM2.17.1, FF21, TB17.O.5, IE8.0, Google Chrome 27, Ghostwall , Avast 8.0.1, JRE1.7_21.