Even though I have a Smart Case, I only use that when I know I'll be taking it out and wanting to prop it up since I hate the feel and the extra heft when it's in the case. When I'm at home it stays in a sleeve and gets used naked.
I periodically use my iPad without a case, but only when I'm home. I don't want to leave home without it being in a case. I'm sure I would be able to keep it in tact, but it would be much more prone to scratches, etc. Also, I just don't like to take any chances.
I'm always "trying" to use my iPad Air naked but the thing I find difficult is when typing an email or message. It's great naked when just reading or just looking around but typing? A case is best.
Even with the smart case, it really does feel different using the iPad naked. It feels really sleek and thin without the smart case. I snap the case on when I put it down.