I've been playing on my 21:9 monitor and due to the way the game scales on it currently, I wasn't able to see the ladder in the prison area, the HP/FP and some of the cutscene text. I'd suggest forcing the black side bars on all 21:9 resolutions, becasue:

A) Everyone playing on ultrawides will see what they're meant to, since they'll likely pick the max available res offered by default. 

B) Those players won't get a Win8/10 nag notification that they're not at the "optimum" resolution every time they run the game fullscreen.

Definitlely like the game so far.

Thanks for reporting it, indeed I never tested it with a 21:9 monitor, and given how it currently behaves, parts of the screen are definitely cropped. I'll have a look on how to fix it.

If there's no reliable way to do it to get rid of the nag notification, the quickest alternate solution I could think of would to exclude 2560x1080 (for 29") and 3440x1440 (for 34") as options, since both will scale wrong and the 16:9 ratios rezzes put the side bars already. The 16:9 equivalents would be regular 1080 for 29" and 2560x1440 for 34". The nag notification's not as important as the scaling issue, as I'm sure the former can be shut off within the OS properties somewhere.