– Better pick-block functioning in creative mode.
– Dispensers now place minecarts of all types onto rails of all types, and boats into water.
– Animal eggs spawn baby animals instead of adults.
– Armor can be put on to wear by shift-clicking.
It’ll only become an issue when they give us a release build like with 1.2.5. Bukkit doesn’t do snapshot builds. Plus, 1.3 will be the last version of the official Craftbukkit releases, I think. They’ll introduce the Minecraft API with 1.3.