I have a matrix with word wrap enabled on row headers, column headers and values properties of the matrix.
In the desktop the matrix correctly shows the text of the rows with word wrapping in effect. But when I publish to the service the word wrapping is lost on those rows and you have to use a mouse preview to see all the text, or re-size the columns to see all the text.
I dont think this was an issue before the Jan release of the desktop. Presumbly you will need to republish a report to the service using the January desktop version to find out.