I'm saying 'two-thousand and ten'.
I don't really have a reason as such. It's how I say numbers in general. I do say 1910 as 'nineteen-ten', but that's merely a matter of hearing it this way in history lessons and being taught it this way in school in general. I'm big and ugly enough now to say whichever comes out, and that happens to be 'two-thousand and ten'. Also, saying 'nineteen-hundred and ten' is too much of a mouthful.
I guess when it gets to '2110' I'd say 'twenty-one ten', but I doubt I'll be kicking about that decade.