Well, remember that you are interviewing them too. More than whether they take you out to lunch, which isn't generally dispositive in choosing one firm over the other, look at what they did to make you feel comfortable and how well you got along with them. For a 3-4 hour callback that doesn't include a lunch or dinner, I would think the least they can do is offer you some water (and trust me, after talking for that long, you will need it!) or a snack.
I know that I was unimpressed by a firm that took me to a local bar/restaurant as opposed to another which took me to a local country club. But, that wasn't the only thing that factored into my decision; it was one of them.