Hey mate.
Don't know if you've already solved your X10 blur camera problem.
But that happened to me too.
Thing is, when I wanted to shoot a i.e landscape, city, cars etc. (from a distance) where the focus has to be on everything, I choosed Single Autofocus & Multi Autofocus - Which gave me blurred pics.
So for pictures like that, I found out that the Infinity focus mode, was the one for those types.
(Funny thing you mentioned the K800i - I had that one before X10 too. The camera was the best!)
Don't know if you've already solved your X10 blur camera problem.
But that happened to me too.
Thing is, when I wanted to shoot a i.e landscape, city, cars etc. (from a distance) where the focus has to be on everything, I choosed Single Autofocus & Multi Autofocus - Which gave me blurred pics.
So for pictures like that, I found out that the Infinity focus mode, was the one for those types.
(Funny thing you mentioned the K800i - I had that one before X10 too. The camera was the best!)