I've just been using 1.8 because I started this world in 1.8 before the 1.9 prerelease and have gone exploring a bit to ensure that I have a sizable map that doesn't get forgeted over by terrain gen when the 1.9 full release comes out.
When I'm done building stuff I will probably upgrade to 1.9 before starting a new world.
Maybe make some kind of Snowy base.