Hi EvanP,
I know there are some people who believe this but I’m certainly not one of them. Because it can result in pelvic tilting and pressure points … it would not only be uncomfortable for most people but could be harmful as well because the spine isn’t supported in its natural alignment. To some degree this may be “less harmful” for a back sleeper but a sleeping surface that is too firm provides poor support/alignment for the body. There are some cultures (such as Japan and parts of Asia) where people use this type of sleeping system much more because they tend to have a much higher percentage of back sleepers than the west and because of physiological differences their pelvis doesn’t naturally tilt as much when they sleep on a firm surface but this is not the case for most people in the western world.
Of course it’s also true that what works best for “most” people may not work well for “some” people and if your experience indicates that you sleep better and more deeply on a firm surface compared to a sleeping surface that provides more contouring support then that may be what’s best for you regardless of how suitable it may be for anyone else.
I’m glad you found us 
You’ve probably already seen this but just in case you haven’t … the tutorial post here is the best place to start.
Good luck in your search and I’m looking forward to finding out what you end up deciding … and of course any comments or questions you may have along the way.
Phoenix