Well, during my time testing out the recent 1.2 update, I am happy to report the following:
- The mob AI for zombies, skeletons, and creepers have improved (they follow routes and avoid dangers to get to the player, so leading them into traps might become more difficult). All other mobs behave as expected
- The new mob drops (iron, gold, and enchanted items) are, in fact, rare (I've only gotten two iron shovels and a bow at this point)
- The world is much larger, which accounts to more mining exploring, and more bizarre landforms. However, since they introduced a sound file for lava, digging near the bedrock level amounts to a fair bit of lag
All in all, I think it looks to be somewhat promising.