45nm (less power, less heat), new case and motherboard design (better airflow), one large fan and quieter DVD drive to reduce noise output, reduced active and standby power draw. It should be far more reliable because of the improved thermal situation.
To the PS3:
XBL is nicer than PSN in a few ways (notably the store interface and Parties/cross-game chat) but costs money, games are always whatever you prefer.
Still doesn't have a BD drive. You could make the argument that a dedicated blu-ray player is more convenient (speed and whatever else), but you still need to factor in the extra cost if you want both. I just bought one for $100, so they're not too awful any more.
Overall, definitely a good buy if you're consoleless.