Honestly, I make a point not to buy WC, however we do have about 6 WC T's in our collection. Mites are often an issue on WC tarantulas, but the benefit of WC T's is fresh genetics. If you're worried about any parasites/diseases transferring to your other T's, you could always just keep it away from your collection until it molts just to ensure that everything is okay.
As far as behaviour and eating go, I haven't really noticed much difference. Of course, WC specimens are usually at least subadults, so they're not going to eat nearly as much as slings or juvies...especially Aphonopelmas who don't eat as ravenously to begin with (in my experience).
Some people are really against WC just because taking the animal out of their natural habitat, and so on. But if it's for sale, and you don't buy it, someone else will. It would be different if you only bought WC T's, but if you want a larger T but don't want to pay tons of money for it, WC is often the way to go. Buying CB is more expensive for a reason: less of a risk of problems. You just need to remember that they're could be underlying issues, and quarantining is always a good idea until you're sure that it's safe to put with the rest of your collection.