i think people are concerned with the safety of crib bumpers because they are worried the baby will suffocate if they get pressed up against it. i don't know how a baby young enough to not be able to move their face if they are not breathing will be able to roll enough on a flat surface to get into a suffocation position anyway.
my baby has maybe slept about 40 mintues total napping in his own crib in 7 months, but i initially tied the crib bumpers to the outside of the crib because I didn't want to use them inside (my new mom nervousness beat out my rational side..) and they still looked cute, but now that he's bigger and i put him in there to play while i do dishes/laundry etc put them back on the inside. i like that if he falls over he doesnt hit his head on those crib bars.
honestly, i don't think its a huge concern. i personally think they look really cute in a crib. if you like them, use them. but if they make you too nervous, just hang them up like a decoration until baby has better control.