Post 2.3, you need 15% less XP for 58->59 and 59->60, combined with the already nice BC quest XP in a place like Hellfire peninsula, mmmm fast leveling AND you can get started on the BC gear.

I can see the advantages on a PvP server, however. I play my shammy team on non-peak hours on our server (PvP), so I rarely have trouble, but I can appreciate a "grab BC loot and head back to Azeroth" strategy.

My whole guild is so excited about my little guys that I'm sure I'll just have a whole slew of people to run me through the first few instances... that's my plan and I'm sticking to it.