Mabey they finally brought the multi device switch button back to the top side. Its useless underneath and flow can be hit or miss depending on set up

Looks like it still has the pronounced hump over the battery LED like the 3 and 3S, so I won't be buying it. That hump causes me significant hand problems I don't have with the 2S and earlier models.

For me the mx master line feels comfortable to use but the weight of the mouse I'm not a fan of. To me it feels like using a brick. Makes sense since at home I use a g pro superlight and at work a g502

Garbage design choice on the thumb rest, because now that is has a crevice, it will attract and keep dirt. Will be keeping the 3S for the time being.

I had the MX3S, now and expensive paper weight. The product had a wide spread issue of the left/right buttons not working after a year or so of daily use. It wouldn't be a problem if the switches were commonly used or could be purchased easily at a reasonable rate. Very few 3rd party repair shops are ready to repair this mouse because the switches are hard to get. I hope the MX4 (like the MX2/2S) use common switches which can be obtained easily it would be great.

It needs at least 1000hz polling rate, the 3s and 3 only have 125hz and it feels super jancky to use

Oh look. An AI button. How do I know it's an AI button? It looks like a butt.