I have a Samsung Curved-Edge monitor. I use it to play osu! and it works out fine. The curve doesn't affect anything with lag or stutters. The only thing it will affect is framerate if the monitor is quite big and your computer isn't very strong. (Though this can easily be fixed by turning off useless graphic settings on your PC and osu! settings)\
In my opinion, I actually prefer to play with a curved screen because it makes the gameplay more immerse, which makes you less likely to get distracted by trinkets around your desk.
In short, curved monitors don't make a difference in delay and input because the pixels are just placed differently. I'd definitely recommend buying one because they usually cost the same as a regular monitor.