I've gone from i3 -> sway -> i3. Maybe it has gotten better since I last used it; but generally I disliked it.
There are 3 distinct issues I've had (one of which I believe was a Wayland-related problem).
(1) I dislike how you can resize a window horizontal & vertical at the same time. Grab a corner, and adjust. I distinctly think that this is a feature and not a bug, I just don't like it. I vastly prefer i3's method of 'Adjust vertical' OR 'Adjust Horizontal' depending on where your mouse is.
(2) Window-title bar. The size of the font/title bar dynamically changing. Lets say I have firefox open with 3 xterm windows in a even 2x2 matrix. I might have 10 Tabs in Firefox open. As I cycle through the firefox tabs the height of the title-bar changes to reflect the website name. With some sites the font size and/or style changes (from default) too. This causes the titlebar size to change by 1-2 pixels. That causes a screen refresh/redraw and my 2x2 window matrix is no longer 'aligned'. The lack of alignment doesn't bother me, but the 'flicker' it causes does.
(3) Wayland specific: screenshots. I need to be able to take screenshots for parts of my job. I've worked around most of these issues (FireFox has a screenshot tool built-in,etc..) but once in a while I'll need to grab an xterm or something else. [ok this has just devolved into a rant.]
I only have one 4k screen, and had some issues with scaling, but I'd be willing to take another stab at Sway.