theres nothing wrong with that bathroom shot.
one of them pictures you posted is a result of camera shake.
You are taking the right proceedures to ensure a a steady shot.
Also note where your focus point is.
Yeah but the bathroom shot is a closeup shot
http://forums.overclockers.co.uk/showthread.php?t=17895006&highlight=101
All pics there mostly taken with the sigma and I never noticed a problem though as they are all decent and sharp. Something goes wrong when you focus further away.
sid