I installed this on WordPress version... ooh, quite young... yes, it's not been updated, but what is there to update? I installed it again when I migrated to 3.5.1 on a new server (and migrated all my data) and it just worked.
It's one of those fit and forget solutions, I didn't even know I needed it until I checked my posts and they were showing markdown in the body. So I went off and found it - I was a bit apprehensive at first because the WP site says it's old and not updated, but it installed fine and immediately my posts were displaying as they should.
I'll probably completely forget about it again and when I next migrate my site I'll be chasing all over the web trying to find it again.
I've not tried any of the other markdown plugins so I can't say how it performs in comparison. All I know is that I can write my (infrequent) posts in a text editor, in markdown, upload it and it displays right and the links work.
Does exactly what it says on the can.