I've seriously considered rerolling the character, on the basis of an ugly character model, a few weeks before Wrath's announced release and take it straight to 80. At least I could use my current paladin as a healbot while running through the first few zones of Northrend. I'm sure there are dozens of reasons you may consider rerolling or maybe just switching your main to one of your alternative 70s.
There is also the Death Knight class, which promises to steal a lot of people's attention for the first few months of WoW. Hopefully only a good handful of people pick up this class and keep Northrend clean for at least a little while. Be forewarned though, there will be tons of Death Knights doing exactly what you're doing, all looking for healers from 60-70.
Have you considered rerolling, switching your main to an existing alt or focusing completely on a Death Knight? For what reason, and are you really going to do it? Please share with us what you plan to do.