never used one but i always thought small height will force photo editor to reduce image significantly for full view of image, on the other hand wide screens look like must have for panorama shots, editing timelines, organizing, spreadsheets and games.
+1 And on the other end of the spectrum I've really liked having 3:2 display for photo editing and web browsing. I prefer the taller aspect ratio for spreadsheets as well but that would depend on how many columns you use.
I could see having a larger ultrawide for use in place of dual monitors with it set off center but that would be the main draw for me.
I've been using ultra-wide monitors for the last six years, including some of the very first 21:9 ratio LG monitors. In total, I have three: 2 LG and 1 Samsung.
I find that the most critical aspect for me is the picture quality of the IPS panel (instead of TFT). For photo editing, that is the only type of the panel I would recommend as it reproduces the most natural colors at has a wider viewing angle without color shift.
Backlight bleeding (in the corners) is a common problem with curved monitors, but some of the latest models have mostly solved this issue. As far as flat vs. curved, I would recommend curved as the picture feels more natural. Since you already have two monitors, you can try that by positioning them flat and then at a slight angle to each other.
The prices for the ultra-wide monitors have come down significantly even within last year. Right now, most of them have deep discounts.
As far as size, I would go with 34" monitor. This size seems to be in a sweet spot between 27" (too small) and 38" (much more expensive). If the budget allows and you have enough desk space, then 49" is a killer monitor.
I'd love to help you more with monitor selection and any specific questions you might have.
I visited a customer a few weeks ago....he has a big desk and not alot to do. LOL He has the full Adobe Suite but he only dabbles. He loves his.....I think for me.....I have three monitors and I like the visual separation. I check email and use for misc. on the left one, I do all my design on my best middle one, and I do all my web work via Chrome on the right third one. To me, having all that one screen would be difficult. But, I think they are badazz looking for sure.
The real power of an ultra-wide monitor comes to life once you've mastered window snapping. Many ultra-wide monitors come with free windows management software. I use Divvy on a Mac with custom keyboard shortcuts to snap two windows side-by-side or three windows side-by-side. This way, I can quickly move any particular program to the side of the screen and have it perfectly aligned.
I also extensively use "spaces" in MacOS and multiple desktops on Windows 10 for each task. One desktop for Editing (Lightroom), one Work (Mail + Slack + Chrome), one for Browsing and Music (Finder + Spotify + Firefox).
The beauty of having triple windows and have a consistent location for each is that it is easy to switch tasks by changing desktops. It is like having three dedicated monitors for each job, ready with a swipe.