EinStein's is a great bar if you a local of a Katy. Not just currently live there but grew up there and went to high school there. Everyone there knows everyone from high school and you feel as though you have stepped back into those days with the clicks and the groups that hang out there.
As a non-local you really aren't treated the same by the other people there. They don't extend themselves to talk to you.
As far as the bar itself, well it is great, it is a bar...but I have been to more friendly environments. The only we way we would return is if I went with a local or we had a big group of friends to where we don't have to worry about talking to others.
It always has a crowd though and not too bad a location...you have to sneak around the corner to find it. If living in Katy I would defiantly visit it once to see if it is your thing. It is one of the better and more tame bars in the immediate area.