Flexable displays are mostly useless for most things I have seen it advertised for.
For phones it is neat because it allows for much thinner designs, lower power, no backlight, and it would be very resilient to drops and falls. But the price would be astronomical at launch, and it will never be used in a way where it is actively flexed. The flexibility will just be used as a shock absorber.
For roll-out tablets it seems like a neat idea, but one of the largest complaints about ultrabooks is that they are flimsy and not ridged enough to use with touch... and that has a backing! A Roll-out display may look cool, but it will probably be annoying to use.
But, there are some things which could be really neat uses for it... once the price comes down.
Devices like Occulous Rift could use them as their displays. It would cut down on the weight (no backlight needed), and the display could curve with the eye, potentially allowing for less optics (weight and thickness).
Large monitors could also be curved, making them easier on the eyes, and more immersive. Right now I have a 28" display, and while I normally sit a good 3.5' away (which is why I got such a large screen), I occasionally sit much closer to it for games. When I sit a more 'normal' viewing distance of ~2' away there are some serious issues of the center of the screen being much closer than the corners. My next monitor will probably be a small 4K TV in the 35-45" range, and with that size I would imagine that I will have similar issues when sitting far away. It would be no good for a multi-user device (like a living room TV), but for a personal screen it could potentially make things a bit easier on the eyes.
Future cars could also make great use of this, especially if it is fairly transparent when not used. Sun in your eyes? You can have an auto-adjusting visor that obstructs the sun, but nothing else... and for every passenger in the car. You could have a map overlay so that you do not need to worry about missing a turn, or worry about stupid localities that use tiny fonts for their street signs. Businesses and addresses can be clearly marked and labeled so that you do not need to worry about looking for small storefront signs when in an unfimiliar area. Stop-lights and signs can be much more blatent. Cars and objects at night could be outlined or brightened up so that you can easily see them. Dash instruments, review mirrors, etc could be displayed in a smaller area allowing for less blind spots, and to monitor multiple points of interest more easily. And we could do all of that while still using an oddly curved and aerodynamic windshield.
But the point is that while there could be a few really amazing uses for this tech, cell phones and tablets are not them. They could gain durability, but they are not going to revolutionize the portable market.