With my Shaman rapidly rising through the levels (54 almost 55 at the time of this article) I've been exploring some of the old world content that I've never seen on my past two 70s. Leveling in Searing Gorge and the Burning Steppes allowed me to skip Un'goro Crater so far (I hate Un'goro), and I've make a few trips into Blackrock Mountain, which I've never done before.
My friend from high school, and fellow WoW player, Breize, who has been leveling as a Boomkin since leaving the server where we both previously played, was a hardcore raider back in the days before BC, and saw everything from MC all the way to the first few bosses in Naxx. Since he knows a lot of these instances inside and out, myself, his Boomkin (who is about the same level as my Shaman), and various other mid 50 and 70 characters ventured into BRD, UBRS, and UD Strath over the past week. Of these, the only ones I had ever entered were Strath and BRD, though my BRD pug collapsed after 20 minutes, so I never saw anything.
Perhaps it's just the beginnings of my weariness with the raid content in BC, but these old instances were a chance to see something new (new for me at least). In addition to seeing the sights, the XP from killing mobs is good, and the XP from the dungeon quests is almost criminal. Absolutely get all the dungeon quests you can if you are entering an old world instance.
One experience that merits a special mention was entering the Rookery in UBRS. For those of you who don't know, the Rookery is the location of the famous (infamous?) Leeroy Jenkins video. In fact, as we were completing the boss event, a few of those in the raid began quoting the opening lines of the video, and a discussion of the loot the Leeroy was after started up. Lo and behold, the Devout Mantle, the very shoulders that Leeroy needed to help him heal better, dropped, and Breize took them as a trophy for his bank (I rolled on them as well for the shear laugh value, but Breize won).
For anyone leveling now, especially those who started playing after BC came out, I highly recommend running some of these instances. A run through by a few 70s is always nice, but if you can find a good five man, I'd recommend that even more.
For Leeroooooooooooooooy Jeenkiiiiiins!!!1!11!!