Just want to see which version people prefer now. Today, you've got Blood, 2H and DW Frost, and Unholy. Unholy is a good bit behind Frost and nobody actually plays it in competitive PvE.
WotlK you could do any spec DW or 2H I believe. Tanking could be achieved in any spec or min/maxing using all 3, putting points in certain locations of each tree, etc. Also there was DW Unholy, I'm pretty sure. As DPS.