I ride on them; I race on them. I've used them for most of the mileage shown in my sig. (S33 Pro, Elite Ride 23 & Elite Ride 25)

My worst accident on the bike happened in a 90 degree turn when the front tire suddenly went flat. It was NOT a Tufo tubular clincher. It was a Michelin Pro 2 and tube. I went back to Tufo right after that incident.

On a couple of occassions I've had a puncture big enough where the sealant wasn't working. I've ridden a flat Tufo tubular clincher tire 10 miles before finally stopping and changing it out for my spare.

During my last race, apparently I picked up a piece of glass. I didn't know it because the Tufo sealant stopped the leak, but the tire was only holding about 40 psi--enough to finish the race. Once at home, I was able to clean up the cut area and place some ShoeGoo into it, letting it cure overnight. Also, I placed more sealant into it. The next morning it held 100 psi. I used that tire another week before I ran over something else that caused it to have a puncture that wouldn't stay sealed at 100 psi, so I replaced it.

Take care when mounting it, especially in the stem area. Use a little bit of soapy water to get the bead started. At final inspection, make sure that the bead is seated properly all of the way around on both sides. If you miss an unseated area, the tire usually stays on, but you'll have a noticeable "hop" while riding.

Tests with tubular clinchers show that the best rolling resistance occurs at >140 psi, but the ride may become harsher as well. I believe you have to consider bike frame material too (i.e., carbon vs. alloy or steel or Ti). YMMV.