Outland at 58 and Northrend at 68 ?

There is a lot of controversy on WoW forums about this issue: Is it a good idea to go to Outland at 58 and to Northrend at 68?

Well, to be honest, I did jump through the Dark Portal as soon as my DK dinged 58 and had no problem whatsoever. I will also go to Northrend at 68 (I already did so with my other characters and had no problems). However, you have to move fast and find the quests that are available for you at those levels. And that can be a problem, 'cause they aren't many. Jame from WoW-Pro has an interesting post on her blog explaining why you shouldn't do like I did and rush to Outland/Northrend.

It's up to you to decide.