Several years ago I purchased a couple of sets to put on a road bike that I used for quick lunchtime rides so that I wouldn't have to worry about getting back to work late due to a flat (sorry cant remember the brand). I recall that they came in three different consistencies to simulate different "psi" inflations. I like my road tires hard so I got the hardest. MAN...there were like rocks. I was like riding on an old wooden wagon wheel. So I ordered the softest ones and those were still quite hard. But, I used them for a while. As others mentioned...they are slower because of a greater rolling resistance. Additionally, any bumps you hit are not dissipated as efficiently as pneumatic tires...meaning more of the impact is taken by the wheel, frame, your body, etc. And I mean you can really feel every little bump!!! BUT, I'd say that if time/speed is not a concern, and you will be riding on a completely smooth surface free of potholes and cracks...then maybe they can be a functional alternative for you. FWIW...I used mine for about a year. Took them off and haven't used them since.

Dan