Bumpbands were a real lifesaver for me during pregnancy and after pregnancy, Im a small framed person so it took me quite a while to really fit into maternity clothes, my normal clothes were getting too tight yet maternity clothes drowned me, I think most people seem to have that stage but for me it seemed to last ages.
I got mine from Newlook for a 3 pack and it cost around £10 which I think is great, in the pack I had one black, one grey and one white.
I used them religously, I could easily use them when my trousers were starting to get abit tight I could leave the button undone and use a bumpband to disguise what I had done. I could also use them to cover the gap when normal tops were starting to get a little short I wore them underneath my other top so it looked like I was wearing a long vest instead of having skin on show all the time, which lets face it no one wants to see.
after my pregnancy was over it obviously took a little while to get back into my other clothes, especially after a c-section I didnt want anything too tight rubbing on my wound, but I couldnt wear maternity wear for too long as it had got too big again, so I was back to using the bump bands to help me out.

I have also seen people use them as a breastfeeding aid to wear under a top so they could lift there top to feed and have the bump band in place so as to not reveal too much skin.