The data from the WMAP satellite that mapped the cosmic microwave background radiation seems to prove that the universe is infinite and constantly expanding. It is flat, Euclidean space where parallel lines will never meet and triangles have angles that sum to 180 degrees. Of course, I'm sure some brain somewhere will find a new interpretation of the data.
Not to disagree, or even to try to expound a sense of what the universe "is," the word "infinite" can be applied to mass as well as to length/distance. I don't think a measurement of the background microwave radiation allows one to conclude the mass of the universe is infinite.