I've been playing it with six other people at my house this way since the patch came out.
I can absolutely understand, also subscribe to, and really do appreciate a general expectation and push to excel and improve... that's the only way anything ever does. However in my opinion, to deem what looks to be pretty decent results as "unplayable" is bloody ridiculous.
The game cuts off a majority of the viewing area, instead of expanding it. You may have more pixels, but the game essentially wipes out 2/3rds of your viewing area. That's not a decent result, that's absolutely horrific. You're wearing blinders, because you're not looking at the side screens either.
If you like to play it like that, fine. But this website exists to help foster and support correct widescreen implementation, and this game does the exact opposite. Compared to a 16:10 screen, you're seeing less vertical and the same horizontal FOVs. Of course you're not staring at the side screens, so you may as well be just looking at a very narrow rectangle in the center of a 16:10 screen.
You may like to play it like that, but just because it supports the resolution doesn't mean it's good support. You can play the game with binoculars to achieve a similar result.
At the end, it's all what your preference is. But as far as letting you see more with Triplehead (as it was designed), it forces you to see less. Which is a far worse solution, both technically and practically.