I take it we’re talking mate as in sexual partner here.
Emotional stability is pretty important for me – someone who understands that I have depression and anxiety and what that means for me and our relationship.
Sexual compatibility I would think goes without saying. I’m kinky and my partner would need to be a Dominant, preferably experienced and we can fulfil each other’s needs.
Geekiness. If I’m spending my life with someone we need to have similar taste in movies and tv – I love being able to curl up on the couch with someone and watch a DVD with them.