It's been a long time since I originally leveled my Death Knight. When I first leveled him, back in the early days of Wrath, Blood was the optimal leveling spec. Now, with the release of Cataclysm, all that has changed. Blood is now the tanking spec and what seems to be the best leveling spec is unholy.
Interestingly enough, it doesn't really seem to change that much about the ease with which Death Knights can mow through questing content. The addition of a permanent pet only helps things. I'm lacking a lot of the self-healing abilities that I remember fondly from Blood, so I'm having to sit and eat or bandage more often than I remember, but other than that, things have been remarkably smooth.
I've also been having lots of fun popping Army of the Dead on some of those elite quest bosses. It's really complete overkill, but it's fun, so I don't really care.
I've also been working on his Mining and Blacksmithing a bit (so I expect his leveling time to fall behind the priest). There's a lot more Obsidium in Hyjal than I remember. Might have something to do with the fact that the last time I leveled a miner through Hyjal was on launch day. Could be that.
So, all in, I've managed to get the Death Knight to level 82 and he's working his way through Deepholm.
I also finally got my epic trinket from Hellscream's Reach / Tol Barad on my warlock, so I'm pretty much just focused on Dragonmaw and Ramkahen dailies as well as the fishing and cooking dailies now. My ability to run heroics continues to be extremely limited, but hopefully I can rectify that soon and power through the rest of that Ramkahen rep.