I'll be honest, the way this is looking with the BtB uncertainty, and the possible issues with single player being buggy, I may just have to move my main focus to smp. Honestly, that's not really a bad thing per-say, I'll hold off judgement to see how much better smp is first I guess. I really didn't like this part in the bad,
Minecraft 1.3: The Bad
Since single-player has been turned into a shell on top of a background server, the game’s resource requirements have increased. When playing single-player, the game needs to be able to both simulate and emulate the world, which take many more CPU cycles. We’re working on optimizing rendering, but those improvements will not be included until Minecraft 1.4.
I am especially worried about this,
Please check your piston contraptions. Most we’ve tested still work fine, but some require changes to repeater delays and similar. Overall, pistons should have fewer bugs, but will appear to update slightly slower.
I understand they want to stop the sand duplication, but is preventing cheaty sand a big enough problem making it worth possibly destroying huge complex and amazing redstone creations?
I am crossing my fingers that this is only Chicken Little, the sky is falling type stuff, and its actually going to get better, lol.