As far as I know, it isn't. My experience is a bit dated, I have visited several times between 2002 and 2006.
A few people were to be seen around the basilica and the museum, the smaller sites were utterly deserted.
By all means go, it's a fantastic place to visit. But do your homework and/or bring a map, the interesting bits are scattered all over the place and not well marked.
Lots of interesting stuff in the region to see as well. PM me if you need more info, I don't come here very often.