I have been using a cuben tarp that I built with another member since the start of my thru-hike. I have had no issues. If you get a hole in a cuben tarp, it can be patched easily with tape. The Mylar tape that Quest sells is great for sealing a tear or a hole if you get one, but I have not had to cross that bridge yet with daily use of my Cuben fiber tarp. There are better tapes and glues to use, but even packing tape or duct tape will patch cuben in a pinch. Any tarp can get a hole in it, but try to patch silnylon! Nothing sticks to it, and it basically requires a patch to be sewn over the offending hole, which then requires more seam sealing. Same with Spinn, although C3 tape works well for adhering a patch to a Spinn tarp.
It is a common misconception that Cuben does not stretch. It does, just very, very little. Rub something against the edge of a very tightly pitched cuben tarp, like your hammock suspension, and you will see the stretch in the fabric - it will definitely warp. This, I have experienced. Through pitching as tightly as possible, the stretched edge has reformed to its original shape. This is my experience, and I have been using it almost daily since March 27th.
A cuben tarp should be pitched as tight as the tie-outs allow. The tie-outs and ridgeline are the most important part of any tarp, especially cuben fiber, and allow you to pitch the tarp as tight as you are comfortable in doing. I pitch mine like a drum - as tight as I can reef it down. Most people do not sew the ridgeline on Cuben (One of the tarp makers does on their tarps, hence the need to seam seal,) because in stress tests on cuben, it usually ends up failing at the sew lines. If the seam is sewn and taped, cuben normally fails at the edge of the taped seam, not at the seam. Same goes with glued/sewn. Sewing is overkill on a cuben tarp, and used to make it pretty (and more easily and cheaply,) for the most part. My tarp is sewn, then overlaid with a 1" strip of 1-sided mylar tape, so I will never have to seam seal.
With any tarp, there are durability issues. Silnylon eventually loses it's waterproofing over time, as does Spinn. If you use one daily, stuffing and re-stuffing, the creases that are created become weaknesses in the coating of the fabrics. Most people never notice it, because most people only take their tarps out for a weekend at a time, maybe a couple times a year. I say most - many people have done thru-hikes with sil or spinn tarps, and have not had an issue for the whole hike. I have certainly never heard, or yet experienced anyone's tarp failing from daily use. The same goes for cuben. Over time, eventually, all fabrics will fail from repeated use. There are different grades of spinn, and different grades of silnylon, and different grades of cuben fiber. The biggest difference between them all is the weight for comparable strength. You pay more for cuben because in comparable weights it is more durable than spinn or silnylon, and you can use a lot lighter cuben fiber to get the same durability as comparable spinn or silnylon. There is a reason all the tarp manufacturers are looking at cuben, and one of those is how completely waterproof it is for how light and durable it can be. It will always be cheaper to go with spinn or sil, and that is not a bad thing for those just wanting a tarp to keep them dry for the 2 or 3 or 10 outings they do per year. Cuben's biggest selling points are how light it is, its durability and waterproof qualities after repeated use, and how easy it is to patch if something ever does punch a hole in it. Also, it does not absorb water like silnylon. Ever pack a silnylon tarp after a night of steady rain? It weighs twice as much (slight exaggeration) because it does soak in some moisture into the fabric.
Tie-outs and cat-cuts. True, cuben stretches very little (see previous point,) and probably does not require a cat-cut as much as a silnylon tarp. And a poorly planned tie-out at an incorrect angle from the cat-cut may cause floppy edges, along with other factors. It has to do with the angle of the tie-outs on a cat-cut tarp, and the angle that you use to stake out your tarp. Believe me, I have pitched this tarp in as many conceivable ways as possible, and I have seen said floppy edge - but if I reposition a tie-out so it is in a correct line with the cat-cut tie-out, the flop goes away. If the cat and the tie-out don't agree, the angle of the tarp line may just need to be adjusted to take care of the issue. That, and not being afraid to pitch the tarp tight. I trust my tie-outs completely, because I have tested the materials and bonding methods, as well as testing in the real life conditions of the AT. I pitched my cuben tarp in 30-40 mph winds at Overmountain shelter in a hawthorn grove in the dark, and never had a flap from the tarp the entire night until a stake pulled out in the middle of the night from the gusts of wind coming straight up the valley. My hammock was swinging from the wind, but my tarp didn't move - the ground failed me. I can't even imagine the problems I would have had with a sil tarp with the stretchiness of sil in that wind! I did it because I wanted to test the tarp in those conditions, to feel comfortable in it's durability. Personally, I like a rectangle tarp because you can pitch one end directly to the ground as a wind break, and a cat-cut allows air to get through the gap created by the arch of the cat. But I love how tight I can pitch with the cats, and don't think I would get the same tight pitch from a rectangle, cuben or not. Maybe it would be close or the same, but the cat-cuts are also dead-sexy!
I also don't understand the people who don't like cuben because of the fact that it lets light through. I love watching storms through my tarp, and seeing the stars or the moon. But I am not one of those people who have to have complete darkness to sleep - when I close my eyes, it's dark for some strange reason. I don't lay in my hammock in the direct sun, because I am usually under trees. I'm also walking during the day. And if I do set my hammock up when the sun is out (which I am going to start doing to avoid hiking during the hottest parts of the day,) I don't put a tarp up. But hey, hang your own hammock and hike your own hike. I don't put my tarp up every night, either. If there is not a cloud in the sky when I set up, my tarp stays in my pack. If I have to get up and pitch my tarp, so be it (and I've only had to do that once when I took a gamble that it wouldn't rain.) I'm in a hammock, not in a tent with walls. I like to see what's going on around me, and I don't care if people see me in my hammock. I guess I'm just not shy that way.
Silnylon has it's place - as a low cost, usable solution to keeping rain off you while you lay in your hammock. Spinn as well - though just a little more pricey than silnylon. And both will create the complete dark environment that some people need to be able to sleep. But I will take a cuben tarp over those others any day for any reason - except when using a tarp as a wind block for a fire, or when I go to the BWCA. The fire, because I don't want to tempt fate with the pricier material, and the Boundary Waters because I don't care about weight when I am in a canoe, I want the largest tarp I can get and tarps are used for so many other things than just keeping rain off you. Heck, I've even used one as an impromptu sail. But durability of cuben long term is not something I am worried about after the small amount of testing I did before my thru-hike of different fabrics for the tarp I planned on taking the whole way to Katahdin. I chose cuben for its weight, the fact it can't soak in water like silnylon, the coating and waterproofing is more durable than either sil or spinn long-term through my stress testing, and is easier to patch if something does happen to it.
Just my long-winded .02.