What drove me to play DK? I'm not sure I've ever been asked that before. Well first I had never played a melee class (pre-bc mainly lock, BC mainly healer, then hunter), and while the other classes of the game all had an energy bar of some sort (rage/mana/energy) here was this new class that had unlimited resources (runes) and had the ability to tank. That coupled with the fact that the death knight was one of my favorite things from Warcraft 2, AND the fact that I'm a lore junkie and DKs are a constant part of lore (though Gul'dan's DKs were different from Arthas').
I just tried a DK on beta and I literally quit logging onto my live account. My guildies thought I quit the game! I hadn't, I was on beta trying every single tree.. dpsing and tanking as all three trees. Leveling to 80, starting a new DK and leveling as a different spec. Trying the different races to find out how much I used which racial and which attacking animation I liked (or didn't like).
I began in beta to know absolutely everything I could about being a death knight, I committed to playing one and never rerolling ever again. At the same time I was a guild officer and raid leader, I had to perform better than the average raider. I needed every ounce of dps, even getting to the point of upgrading my computer so I had less lag. I'm not the best DK out there, I'm probably not the best on my own server (or even in my guild, Goosedog is a BEAST), but I'm going to be the absolute best I can and that means going with the spec that gives me the best results.