I think there are a couple of misconceptions here regarding tubeless. It's not as complicated or bothersome as some suggest. Basically it's a regular clincher tire system that doesn't require an inner tube. The rim will have a slightly different "clinch" and the tire a different bead. At the same time the system will also be fully compatible with regular clinchers.
If you get a puncture you can do the following:
1) slip in a regular inner tube
2) patch the inside of the tubeless clincher
3) use liquid sealant
4) put a drop of super glue in puncture hole from the outside. You won't even have to take off the tire.
(I'm not sure about latter two due to the higher pressure. It does work on MTB tires.)
When they're released they should be as easy to mount as a regular clincher. Unlike with sew-ups you won't have to carry a whole spare tire with you and a sewing kit. Higher pressures than 120psi are completely unessary. I ride 100-105 and sometimes even 95 front with Pro Race. Going higher will only make the ride harsher. You can't compare it with sew-up pressurs due to the different design.
The only down side I can think of is weight. After several years of development the MTB versions still are heavier compared to a regular inner tube + tire. I'm skeptical that they'll be able to bring the weight down of the road version to the 240g that was mentioned. However, if they can it's going to be a winning system for sure - as easy to use as a clincher - no bulky spares to take with you - no messing with glue or tape - smoother ride - better reliability - less rolling resistance.
tufo tubular/clincher Jet Elite is 225 grams. so its ligher than the version mentioned above. i think your wrong about it being unnecessary* to ride ride with more than 120psi. when my tufo's fall below 120psi they feel too soft in a sprint or when climbing hard. now i try to keep them at 140 - 150 psi. and even in nyc with all the pot holes they still feel pretty nice. i think/guess it is the design of the tub/clincher tire.
i havent had a chance to use the sealant in the tufo, cause i have yet to flat (i hope i have not talked to soon
) but i hear that it works very good to sealing the tires up nicely, some even report no loss of pressure when used as preventive measure. i think the tires are very puncture resistant. i see alot of nicks and cuts on the tire, but none of them go all the way thru
i think if you want a low weight good functioning clincher with tubular properties, this is the way to go.