Update: Engadget posted a full review of this phone, you can read it here.
Engadget posted a short hands-on review with LG's G Flex curved smartphone. While they like the display and understand that this is just an early stage of curved and flexible displays, they say that "there doesn't seem to be much of a point for people to buy into the idea". Overall it is a pretty good first-gen product, but still a novelty.
Compared to the Galaxy Round, Engadget's reviewer says that Samsung's phone feels better in the hand (he says that the G Flex is very large and pretty uncomfortable in the hand and a little awkward to handle) and it offers a higher-resolution display (even though it is smaller in every dimension).
On the other hand, LG's phone however is more durable - it has the self-healing coating on the back and it can actually be flexed a little - which should make it more resistant to accidental phones or hits.
The reviewr was a bit disappointed that the display is only 720p and not Full-HD. He doesn't understand why LGD didn't go with FHD. It's likely that LG simply was not able to deposit and pattern the OLEDs so precisely. But surely they'll get better at this in the future.