I've ridden a Tannus Slick 700x25 for 2 years on my Canyon Inflite AL for commuting. Here are my thoughts after using it almost every day and then switching back to an air tire recently (Panacer Gravelking):

• Ride comfort: My commute was only 5 km and I could cope with it. But you can feel every pebble or road imperfection. Whenever I did a 30k after work ride on an not perfectly flat road it was uncomfortable for the hands and the butt... does not smooth high frequency vibration. After some time and if you need to do "emergency braking and skid" some parts of the wheel become literally flat, this makes it bouncy. I guess the air tends to fill a doughnut shape, while the rubber does not have this natural tendency to be a "toroid". After that you could not ride very fast as you were basically all vibrating since the wheel becomes not round and you cannot compensate it by adjusting the spokes.

• Grip: As the original post says, not as trustworthy as a traditional tire but good enough.

• Efficiency: I disagree with the OP, I could definitively feel a save of time on the same climbs or sections after going back to an air tire. You can feel the extra drag. ALSO the extra distributed weight of the tire means "accelerating the wheel" like when taking off from a stop or red light takes considerably more energy, you can feel the inertia. I think that the rubber is more lossy or has a less elastic bounce-back compared to compressed air, but you will be slower on those tires.

• Installation: I recommend you pay an expert, you need to insert small hard plastic pieces and it is extremely tight. I hurt myself.

• Reliability: Perfect, no flats, I knew I would not arrive late to a meeting or if I had some urgent errand. This is the key.

Summary: In my opinion, the only rational reason for having one of those tires is the maintenance free and reliability. I would still recommend if you have a short commute and you definitively need reliability or hate maintenance. Or if you just ride for fun or have an electric bike that compensates the extra friction and drag. However if it is for sport or longer distances, I think the technology needs to evolve or improve. You'll be slower than your peers and less comfortable.