First impression. FEEL: The G403 feels as comfortable as the MX518. A few changes I don’t like. I prefer the design of the main two mouse buttons on the MX518, they are party of the body of the mouse and the top/end of the buttons recces into the mouse. The design of the G403 and many current mice have buttons separate from the body and some of them feel loose and have a gap the dust and dirt can enter the mouse through. The side of the G403 feels nicer and the rubber feels more durable. I prefer the style of the MX518 thumb buttons though this is preference. The thumb buttons also feel like they are a little far forward. The cord is a bit stiff but I’m not sure if it will be an issue. SCROLL: The scroll wheel feels like a Lego wheel, not rounded like the MX518. I like the scroll wheel on the G403 more than the MX518, but prefer the wheel on my MX anywhere. The metal wheel does not seem to be common on gaming mice. My MX anywhere is much heavier, so that may be a consideration. The scroll is very smooth and quiet. I can scroll precisely without audible clicks. SENSOR: The sensor is straight up better in every way. I’ve read the angle is different but can’t comment on what effect this has. The DPI of the MX518 was too low, so I had the sensitivity maxed and acceleration turned on in windows. The DPI becomes an issue as monitors increase in resolution. Mouse poling is much higher and the ‘feeling’ is much more accurate though it will take time to get used to it. MX518 DPI - 400, 800, and 1600. G403 DPI – 5 custom presents 200-12000 SOFTWARE: I’m pretty happy with the software, it didn’t take long to set up. You can assign up to 5 DPI settings, assign a default and a shift DPI which is selected when holding down the DPI button. I’m not sure why Logitech went with a single DPI button instead of an up/down. As a result, I’ve only set 3 DPI defaults. LIGHTING: the lighting opens are disappointing. I can set cycle or breathing. With cycle, I can limit the range. With both I can adjust brightness and rate. Breathing has more options but the setting for it are not intuitive and I will need to look up how to adjust them. I would prefer if I could set a range like yellow to red that it would cycle between. OVERALL: The mouse doesn’t feel as solid as I expected, but it is light and comfortable. Lighting is nice but not as customizable as I expected. The feel of the main buttons is nice and the sensor is excellent. I wish the thumb buttons where a little back and that it had an up/down button for DPI, but I may not adjust the DPI much once I get it set just right. The feet are well designed and the mouse feel good to use. The appearance is plain, much better than most ugly Logitech mice. The MX518 is not in a box at the top of my closet.