I got a replacement sent out for my original problem (stiff right click) and my replacement has much better right click, but the Mouse4 shell issue is far more sensitive on my replacement. On my original, I had to push really hard on the sidewall a certain spot to actuate M4, but my replacement requires much less force, so I can see it being a valid complaint for some people that use aggressive grips. Personally doesn't bother me on either copy I had the issue with.
Now I hope they make a shorter version, or something comparable to the G100s, but I have a feeling they're just going to copy Zowie shapes with their own small adjustments. Apparently they're releasing 3 more mice and possibly wireless.