I pretty much use dreamwidth for backing up my LJ fics and the occasional crosspost; if LJ ever goes completely under, at least I have everything important saved over there. And I've noticed a very slow but steady drift of my fandom BFFs over there during the passing years so it's nice to keep all their DW journals friended juuuuuust in case!

Tumblr definitely seems to like quirkier pairings for the most part, which deeply pleases me - Balthazar/Castiel seems a lot more popular on Tumblr than on LJ, thank goodness, because those two had chemistry together and if there wasn't any support for them anywhere I might have to cry a little.