I had one put in once I was asleep and it was taken out the next morning. It wasnt noticeable most of the time but I kept feeling like I needed to pee and when they checked it had just backed up a little bit. I felt as though it was about to fall out but when they removed it the nurse said that there was a little 'balloon' that they had to deflate first so really it was in no danger of coming out. I only got the feeling that I needed to pee a couple of times and it was truly lovely to not have to worry about getting up and down to the toilet and by the time it was taken out I was with it enough to appreciate the walk to the toilet.
It really isnt that bad, I think that people panic about them way more than they need to.
Steph xx
P.S...it didnt hurt when she removed it, wasnt even uncomfy, was just a quick "ooh" moment.