How useful is a glider/rocker?

Can you ladies tell me if you had any experience with a glider/rocker how useful was it? I plan to have the baby in a binet in my bedroom then move him into his crib when he is 3-4 months (maybe longer). Basically the glider will be in the baby's room. I thought it may be useful in there since I'm planning to feed. I need some input before purchasing one because these things are kind of pricey. Help?