Ellicott Mills was one of the first brew pubs I had ever been to, so it set the standard for me of what a brew pub should be like. I've been to many more since then and have found others I like much better, but I still enjoy going to Ellicott Mills.
When we go, it's primarily for the beer. They have some good standards that are almost always on tap (I like the Marzen) and their seasonal beers are often creative and very good. You can get a sampler of small glasses of several of the beers so you can try them all--good for the indecisive. The food is decent but unremarkable, pretty much standard pub food. The service is the same--they always seem to have too few servers but once you get their attention, they are courteous and helpful.
The atmosphere is easygoing--it's fine to walk off the street wearing shorts and a t-shirt to eat here. Don't sit close to the door or you'll be cold in the winter and hot in the summer. If you can, sit upstairs where it's quieter and not drafty.