Baseline (Widescreen) Solution & Issues
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
Eyefinity / Surround Specific Solution & Issues
Multi-monitor is a mix of Hor+ and Vert-. I tried in both full-screen and windowed mode. There are some areas with a limited render area. In these, the game limits the horizontal width, and the game becomes Vert-. I did notice that while changing the resolution from 1920x1080 to 5760x1080 (in one of these areas), the game does initially go Hor+. Once you click the "Resume" menu selection, the camera zooms in to a Vert- view. A screenshot of this is in the "additional screenshots" section. The background used for the initial game menus is Hor+ in multi-monitor.
Additionally the FMV is a 16:9 image stretched, along with the menus. Finally some gameplay areas can become inaccessible in multi-mon (like we saw with Aquaria). Luckily you can change screen res on the fly (without saving or exiting the game), so this is easily overcome.
I'd love to give this game a higher score in multi-mon, as it truly is gorgeous to play. However, there are just too many little issues to ignore.
4k UHD Specific Solution & Issues