This was the third time I have been to the caverns...every time I get a better camera, I keep coming back for more! Luray Caverns is definitely worth seeing if you love nature. The tour is around an hour and involves probably at least a mile of walking. I came later in the day this time and the crowd was bigger than in the past, so I think it may be better to come earlier in the morning if you don't like crowds. I know that some of the other reviews mentioned audio headsets, but every time I have been there has been a real tour guide. I mostly hung toward the back of the group so I could snap some shots with my camera. The tour always moves a little faster than I would like for photography, so I would recommend bracketing (long exposure) and a tripod for the serious photographer to get the most out of it. Tickets may seem a little pricey, but it was definitely worth it for me....and the amount of lighting, etc. they have put into the caves is amazing.
A few tips: wear tennis shoes or other sturdy, non-slip shoes, as some parts of the caverns are still actively growing and the ground can be wet and slick in places. Don't hang back too far- the lights do automatically shut off after a certain amount of time, so be sure to stay with your group!