downsides to optical mice?

So I'm sick of using ball mice, and how easily they gum up even after you clean them.  i've been thinking of getting an optical mouse

do optical mice have any common problems of their own I should know about?

OP, how do you plan on using this mouse? Do you game? If so, try not to bargain-basement it and get something decent. If not, whatever is on sale this week should be splendid.