It appears to me that the /spawnpoint command, while it would in previous versions guarantee that a player will respawn at the exact coordinates it was given (like spawning after sleeping in a bed), now acts like the default spawning (like spawning without ever sleeping in a bed,) respawning the player somewhere near the coordinates it was given. Not sure if this is a bug, but it is surely an unwelcome change in my opinion.
As far as I can tell, this has been fixed as of version 14w03b.