bottle warmer

So I just realized this is something I haven't purchased yet, wondering if it's necessary to have? I will be EBF for the first few months hopefully and then start pumping, my mom said  I can just put the bottle under really hot water and that will warm the milk and I don't need a warmer. But I feel like that would take much longer to do. So if you have a bottle warmer, do you like it? Or if you don't like it, why?