I recieved a fisher-price one as a gift which we used when bub was first born as we were living in a double story and he slept upstairs. Now that we are in our new house and he sleeps in the next room with the door open, we haven't used it once. I still manage to hear every noise he makes- and as baby monitors amplify every sound- we really couldn't handle any more noise!! Plus, as Kell said, you will find your mother instinct is stronger than you think. I seem to always wake about 5 mins before bub- its bizzare. They start to stir long before they cry and I've got bub on the boob before he even has the chance to wake-up fully and cry!! Another thing to consider is that baby monitors omit radiation which can be harmful for bub. Apparently there is a device that you can purchase to minimise the radiation.
However, if you feel that you will have difficulty hearing bub during the day from one end of the house to the other- than you will find a monitor useful.