OP here:
Thanks everyone for the recommendations.After reading your advice, and reading a TON of reviews on the internet, I think we're going to go with the Home Depot Behr Premium Plus Eggshell for the walls, which runs around $22 a gallon. (I decided against the more expensive version with the primer already mixed in, since we will be repainting in a very similar color to what is already on the walls.)
Now for the big question...does this stuff ever go on sale? President's Day weekend is coming up soon, and I'm wondering Home Depot typically runs a paint sale then? I recall that it's always on sale for Memorial Day weekend, but I can't wait that long. We're doing the entire house, so it's going to be a lot of paint.
They sometimes do a $5 per gallon mail in rebate, that's the best I have seen. They just did it a few weeks ago so not sure they will do it again soon.