My son did not have any troubles. We allowed him to pick the one he liked best, (as a 2 day old baby it was a toss up, we tried about 5 or 6 brands and he chose to use the nuk ones)
he will not use one at all now, only his thumb. I did everything I could to keep him from wanting his thumb, I used the onsies with the fold over hand things and even used socks to cover his hands all to no avail. He wants his thumb.
In my opinion it is best to keep his mind straight about the difference in bottle nipples and real ones. We use only the playtex nurser nipples and I watched exactly how he was supposed to be on his moms nipple and I made him do exactly the same thing to get the bottle in his mouth. I would not allow him to eat from his bottle unless his mouth was exactly like it was supposed to be to nurse from mom.
It seemed to help.