I love this mattress, it's amazing and I've been getting much better sleep on it than my previous innerspring mattress. It did take some getting used to for the first week (it's a firm mattress) and I would say the original is probably better for the back sleeper. I'm a side sleeper and have some old injury pain points, so I think I need the upgraded version of this one which is the only reason it does not get 5 stars. I think if you're in good shape and like firm support, this one is perfect for you. I am really benefitting from it and will probably upgrade to the one with more internal support regions once I can afford it. This one fits just about any budget so I highly recommend it as your starting point with the Casper!
The Casper original is the best mattress I have ever slept on. My wife and I love it so much we bought three and recommended to my brother in law, who also purchased one.