ShiftaI was actually a big fan of the sensor position in the g500. I don't know where this idea that perfectly in the middle is the only good place for a sensor. Do you have a pic of the underside of the new mx518?
Mostly because almost every other mouse is really close to the middle putting it far forward or the side makes it unintuitive for users who've used basically any other mouse.
https://i.imgur.com/EVU2TsR.png
just glancing at it compared to a G400s the sensor position is about 0.5 to 1mm closer to the butt of the mouse on the new MX518
stock skates are terrible, was going to replace them with hyperglides anyway but was expecting skates with the rounded edges already like the G403 had, these are pressed flat skates :(
Cable is slightly more flexible than original cables for this design (and no it's not just a age difference in the outer coating of the cable). Diameter is approximately the same. Seems to be mounted better to the front of the mouse.
Clicks feel a bit stiffer than my g400s but that is probably from significant use on my g400s.
DPI buttons are weird the DPI up button feels like it actuates a mechanical switch, but the DPI down and default buttons feel like membrane like the G400s and older mice.
Scroll is similar but different not sure if this is a difference I created when I messed with the internals of my g400s including the scroll though. Scroll on my g400s has a more obvious tactile feel to it while the new mx518 while still noteable isn't as obvious.
Plastic is a bit more textured than the G400/400s except the cover shell which is very glossy like the original mx518.