I am currently a history student at university. We've actually been given Gibbon to read quite a lot over the course, but mainly for the study of historiography and as a way of demonstrating how far our understanding of the past has come since Gibbon was writing. So, no, it's not studied for factual information. There are much better sources to use for general facts than Gibbon's Decline and Fall.

No. Knowledge and understanding of the past has simply moved on so far, that works from that works like this simply aren't very useful for anything but historiography.