The first crack in that sense of disdain for the class was the starting zone experience. Anyone who's done it knows it's one heck of a well designed start to finish piece of gameplay. It was so well done, in fact, that I actually rerolled several DK's in an attempt to find the one race I really liked, secure in the knowledge that not only would I start at level 55 and be Outland ready by the end, but I'd enjoy the trip. After that, I blew through Outland on a Tauren, Gnome, Draenei and Dwarf before finally settling on my Night Elf here. Heirloom shoulders made the already painless starting zone even more rapid and Outland fell away like a solid fuel booster rocket lifting me to Northrend before I'd even finished Nagrand.
Now here I am at level 80, and for once I actually have a third alt at max level (not counting the old days when I had four level 60/level 70 warriors - I'm sad to report I only have three 80 warriors now) of a different class. Gearing the DK's been interesting, and as I've run myself through various content my DPS has been steadily increasing, my understanding of my specs steadily expanding (frankly, I love Blood as a DPS spec, it has so many cooldowns for AoE damage and a nice bag of tricks without being as fiddly as Unholy, and I can't say enough good things about Frost as a tank spec) - I have to admit, I've totally turned around on DKs. They're awfully broken in my eyes (even after the most recent nerfs to their cooldowns and tanking health) but I cannot pretend to be having a bad time playing the class.
So now I turn to you. What class turned out to be a surprise hit with you once you tried it out?