We did the first 2 Instances of the Hellfire Citadel. The atmosphere was pretty nice, the instances not very hard and the loot was decent.
Shifting Sash, Blood Etched Shoulders, Bloodstained Ravager Gauntlets, Auslese Light Channeler
Some Questrewards for killing Bosses in first intance:
Perfectly Balanced cape, Sure-Step Boots
Also I checked the Rogue Trainer in Stormwind, who was selling Eviscerate 9 and Deadly Poison 5 – those can currently only be trained from books that drop in instances. So its nice to know that You do not need to buy those overpriced books if You have patience to wait for release of Burning Crusade.