Personally, I don’t see much point to flat ultra-wide monitors, especially if you’re at a desk, sitting. This is because, in order to see all of it comfortably, you either have to position it very far in the back (which requires you to have a very wide desk), or you have to have a pretty small monitor (in which case, you may as well have it taller).
Curved ultra-wide monitors make more sense to me, but are a bit weird, in my opinion (and they take up a lot of space in the front-back direction, a bit like the old CRT monitors). Also, they are quite expensive for what is an average or below average picture quality.
I prefer having two identical 32" monitors, normal 16:9 ratio. I have a pair of fairly cheap ones, which are quite nice. For me 2 times 2560×1440 is quite enough – I’m too blind to fully appreciate higher resolutions, and on Linux high DPI is often more trouble than it’s worth.
What I like about this setup is that I can position them at an angle. Depending on how far away from them I am sitting I can adjust that angle (so that my head is in the intersection of the two normals of the rectangles that the screens are): if I am sitting far away, I can increase the angle to be closer to 180°, and if I sit closer, I can make smaller. That way, the monitors can always be perpendicular to my line of sight, which is important, because the optimal viewing angle of these monitors is rather small. This is a bit like having a wide, curved monitor, except adjustable and without all the curved weirdness.
The big downside is that there is a seam between them of about 10 mm, so I use only one when I want to watch a film or play a video game. However, in my opinion, one 32" monitor is quite enough for games and other media. Having two is really nice for productivity.
I think the only situation where an ultra-wide monitor would be better than my setup is for watching films (but only the ones in that format!). When it comes to games and most other media, I think they look better in 16:9. And there is a lot of older games and TV shows that are in 4:3 (as well as some newer hipster films[YouTube]), so any ratio bigger than 16:9 just wastes a half of the screen.
Of course, it should go without saying (but it doesn’t), that this is all my personal preference. I’m quite happy with what I have, but it may not be the best for everyone. My hope is that my ramblings will inspire you to think about your own situation and preferences, it’s not an assertion that my preference is the only right way to do things.