I was pondering this question and wondered what DKs thought about it.
A lot of the Cataclysm experience will be about leveling a new character. A lot of the old 1-60 content is being remade. Now Death Knights obviously start at 55 and hence miss out on most of this experience. It seems a bit of a shame imo as your missing out on one of Catas strong points. Sure, you'll see it once you return from Northrend, but you're still missing a lot.
The leveling experience would also benefit from having another tank class available as anyone using the RDF to level will probably agree.
So what if the whole starting area for Death Knights took place from level 10 to 15 instead of 55-58. Would Death Knights really feel cheated?
Lets face it, the whole "Hero Class" aspect was never a big deal and WotLK is now over. I think the game overall would benefit from having DKs start closer to normal characters.
I realize most leveled DKs might disagree or simply not care, but maybe if you see the broader picture you might be more inclined towards this suggestion.