I'm really torn on the idea of endless rage for the barbarian. I really like the concept of building rage and having to use it for moves. I feel without a rage meter the barb will be an unstoppable killing machine with very little limitations. The new whirlwind animation is pretty solid, though. I'm REALLY disappointed they didn't reveal any new wizard talents. I guess we'll have to wait until Blizzcon 2010 for the final class reveal. I was sort of hoping they'd reveal two new classes. The monk, however, is growing on me. Blizzard said they strive to create an arcade beat-em-up style class, which is pretty neat. It doesn't look like it has a lot of AoE type talents, however. From the gameplay videos I saw, the monk focused a lot on single target attacks.
Also, they didn't cover crafting, runes or the talent system. They basically introduced the monk, showed him kicking ass for about 20 minutes, had technical difficulties with the video feed during the segment in which they showcased new enemies so we ended up seeing a black screen the entire time, then on the second day treated their entire panel as a Q&A