We went with the left rail filters. It did reduce the content area and we played with removing the right rail but for business reasons the smaller content area was the trade off we made. It did make the interaction of the filters much more usable and scalable. The previous design had top filters that had a hard time scaling to show very many filters (food categories for example requires substantial real estate).
This is the sub-filter design. There were some parent filters that needed child filters, if you will. You can see here that when restaurants was clicked there were sub filters that then applied. We didn't want to create another level of cascading filters underneath because the visual hierarchy of filters would be hard to distinguish and take up even more horizontal space.
This was an early concept we considered but ultimately decided against because of several reasons. We knew our users would want to toggle filters frequently so they'd need to be able to view the UI without being buried in a menu. We also couldn't get the menus to elegantly hold and display all the controls necessary for each section.
