Infinite. I find this topic, however, as a misuse of human intelligence. The answer is simple:
If the universe is infinite, then we'll never know it is infinite (being itself infinite won't allow us to know if there's an actual 'end')
If the universe is finite, then the point 'past' the universe should or would be nonexistant. Now I don't wanna talk about nonexistant space for it always gives me a headache.