i bought a pack n play with all the accessories, i don't like cribs, they take up too much room, and all the recalls freak me out. i personally would never use one, but if you do, i see no prob if you take out when they become active. my dd is 9 weeks and already scoot herself around.
I just took the bumpers out of my 17 month old's crib because I didn't want him using them as a booster to climb out of the crib. I never had a problem with them and honestly can't see how a baby can get tangled up in it. I know they say it can happen, but I was never afraid of that.