My new favorite software is Lightzone RT. I'm playing with the free demo because I don't think you can buy it yet (but I hear it will be about $100). http://www.lightcrafts.com/products/lightzone-rt/
This adjusts exposure the same way I think about it in my head (I was weaned on the Zone System). It's deceptively simple looking until you realize you can stack zonemaps and change their blending modes. I haven't even started playing with the bezier masks yet.
I only wish it was available as a Photoshop plugin, and that it could blend individual exposures (ie: tone mapping). It also has a big brother that is more aimed at working with Raw files (the RT version is aimed at TIF and JPG files).