Did test riding years ago on airless tires on our tandem.
Tough to install/remove even with their special mounaing tool.
On super smooth roads, they rode fine.
Once it got bumpier/less perfect surface so was the ride.
Upon crossing a cattleguard (if you live out West you know what they are) it was like riding an eathquake!
I'd rather fix a flat!
Just our experience/opinion.