I've had horrible experiences with Behr. Decent luck with Valspar. My fav is Ben Moore--I'm OK to spend a little extra to not have to put on 3+ coats, yknow?
Sherwin-Williams. Even their less expensive lines have great coverage and are very durable, and they do several 40% off sales a year that make their top of the line paint the same price as Home Depot or Lowe's.
I vote for Benjamin Moore. Paying the extra money for good paint is absolutely worth it. If you get crappy paint then the first time you need to wipe the walls all your time and effort is wasted because now you have a big shiny spot where you wiped.
My favorite is Ben Moore - with that said, our entire house is painted in Behr. Mostly because we LOVE our "paint lady" that works at the local HD. Behr + primer was recently ranked pretty high by consumer reports.
We weren't a fan of Valspar. It took more coats, but DH said he felt like it would just gunk up on the brush/roller insted of spread on the wall.
We use Valspar in a matte finish and have liked it so far. My parents love Benjamin Moore, it's the only paint they'll buy. I've never used Sherwin Williams, but have always heard good things and they have beautiful colors.
I really like Valspar. I've used both the non/low VOC one and the signature (both with primer)
I liked both - we had one room that the renters painted that was a PITA to cover and the signature worked a lot better than the other one, but in other rooms where the crazy paint wasn't used the cheaper one worked perfectly.
I've used BEHR too it's good, the only one I've used recently and hated was olympic.
For color, Benjamin Moore. If cost is an issue, you can get the contractor grade. I've found the quality of even that to be as good as hardware store paint.