The pro is it helps you pattern deer and understand how they move season to season. (It also gets you out of the house and into the woods and that's always a good thing.). The con is you can disrupt deer movement and patterns with cameras (maybe). Deer can see the infra red and hear the camera click. They seem more curious than anything, but who knows. You can minimize this by putting cameras up higher and back a few feet from a trail. You also disrupt deer by walking in and out of an area. Most deer are used to humans around so this isn't usually a big deal.

I have a couple of areas I hunt where I consistently see big bucks and are not generally entered by other people until the December rifle season. I don't put cameras in these areas until September. I leave them for 2 weeks, unchecked then I pull them. I use them to figure out what's in the areas and where I should hunt. The rest of the year I stay out of these areas. I have a lot of woods to walk the dog, etc. (Although if a gobbler sounds of in one of them in a few weeks, all bets are off and I'm heading in).

I leave my cameras out year long, it tells me the buck to doe ratio as well as the number and sex of new borns. The deer herds where I hunt don't seem to be spooked and from the pictures and videos I get ignore the cameras, it really helps to pattern deer movement and shows when new bucks enter a area.