i've been using it for almost 2 years and i find it useful but i also think it's nonsense unless you're playing medic
there's small amount of people who use it because most people don't see the point in changing something that's working
just quickly reading through comments
no need to play in windowed, nvidia, intel (and amd iirc) utilities have "add custom resolution" option (or you can use cru)
there is slightly higher fps variability but shouldn't matter if you're not playing on a toaster
from ETF2L config: sv_restrict_aspect_ratio_fov 0, no clue about ugc/esea
i guess the black bars matter on small monitors and depends how far from monitor you are