I didn't realize they were still making more levels through teh internets, I've got to start playing this game again.
They haven't been releasing too many updates to SMB on XBLA, last one was around January. But hey, they're free, so I'm not complaining if they don't release anymore levels.
And as far for the controls. I have NEVER played a platformer that controlled smoother than this. In an interview Tommy Refenes (programmer of SMB) said that Super Meat Boy started as one level with a cube in it and he wanted to make that cube feel really really good. He succeeded with a Grade A+