My long-neglected Tauren warrior finally hit level 68 this week, making him eligible to depart Outland for Northrend. I did all of the "Horde-specific" quests in Nagrand and Blade's Edge between levels 65-68, though the quotes are necessary because many of those quests were identical to their Alliance counterparts other than the questgiver saying "For the Horde" when you talk to them. I was very disappointed because I had always figured that my fourth trip through Outland (twice on retail, one in the Wrath beta) would feature new and different material, but instead I was simply killing the same mobs for different questgivers more often than not.
I did cheat a little bit in obtaining my Northrend alchemy perks early, but, even so, I was a bit surprised at how easy the content was. I had My Fury spec was less than ideal, but I suppose that the option of swinging a pair of two-handers and glyphing Bloodthirst for double healing didn't even exist back in 2007. I would have expected a cake walk on my home server with a full set of heirlooms across the board. Cut off from all those resources, and left with only the stuff I could pay for with gold from that particular character, the content was still a cake walk. If I want a challenge, I need to aim for mobs 2-3 levels higher than I am, so that the reduced hit rates can kick in and slow my swinging flurry of death down a notch.
In one final note, as nearly as I can tell, Netherstorm and Shadowmoon are both completely obsolete. I had just barely replaced my last pre-Outland item when I hit 68, and I didn't have any trouble jumping into Northrend (where I promptly upgraded those items even further). I remember this jump being tougher during the Wrath beta (I haven't tried it with a level 68 on the live servers), even with the then massively-overpowered Death Knight. Under the circumstances, there's no reason whatsoever to stick around in TBC content, gaining less exp and worse rewards.
Given how slowly Blizzard adds content, it will never fully make sense to me why they make such a point of aiming whole zones in each expansion at players who aren't already at the previous cap. Are there really players who gave up at level 68 and weren't willing to pay for Wrath until they heard that they could skip those last two zones? In Cataclysm in particular, with a relatively smaller amount of the new content allocated for max level characters to begin with, I'm concerned that this will leave not all that much content to go around for the leveling path to 85.