having some problems with it. It will not play any youtube videos with advertisements at the beginning. I tried clearing cache and turning off popup blocker adblock and everything else I can think of. Still no good.
Unless you're using the HTML5 beta, this is most likely an issue with your Flash plugin and not with Firefox. YouTube plays just fine for me with Gnash 0.8.9.
Anyway, I've been using Iceweasel 4 since beta 12. I think it's a really nice improvement on the 3.x series, although for some reason the GNU/kFreeBSD version uses up extortionate amounts of CPU time (the GNU/Linux version is fine, though).