Let's say every game ever has an infinite health cheat - ooh, an option you can use or not! But at the same time it'll basically kill the game's replayability appeal.
Now, in this particular instance, I don't particularly mind one way or the other. It seems like a weakening of the business model, and it does split the playerbase slightly (though not by very much). On the other hand, it's a requested feature that people have already stated they'll gain increased enjoyment out of the game from.
It may yet be a blow to Prophecies (and later Factions, but capping is a lot faster in Cantha) in the long term - the "deserted outposts" syndrome might be exacerbated... We'll see.
Good Job on Anet's part by not letting the new players get left too far behind. |

On the technical side, I'm perfectly happy with the explanation that withdrawing single class unlocks is necessary for coding reasons.
...I wouldn't suggest holding your breath waiting for a Nightfall unlock pack, though. ANet is presumably smart enough to wait for at least one ladder season (in wich Ch3 is legal) so as to - ahem - encourage people on the competitive end of PVP to buy the expansion right away. Why undercut their own product launch?