NONE

Uncomfortable and ergonomically incorrect for most people. Buttons located on the lower sides are in the way and screw up gaming big time. Press the mouse button and It double clicks every time, lots of fun when I want to pause videos but the screen maximizes instead of pausing. This mouse is absolutely useless. It is now in 10,000-plus pieces!!!, now it is useful...lol.

Trash... stay away... Purchase a 5-dollar mouse, it will be way better.

Amazing Battery Life. Included battery barely lasted a week, but a standard Energizer has lasted 6 months and is still going strong. I'm a daily user, and keep it in my work bag. I also switch between multiple computers all day long. Pairing to 2 separate devices via Bluetooth is easy, and works well. Note that I only tried Windows machines. Switches between those devices quickly. Works as exactly as advertised. Very comfortable, even for a 'fingertip grip" user like me.

Needs a case. As of writing, Mem Expr doesn't sell these. You can find 3rd Party cases out there at other online retailers. Included Bluetooth dongle is stored inside the mouse under the battery plate. After 6 months the plate is still inserting firmly, although I am concerned both the plate and dongle will eventually be lost. Price. This mouse is not cheap. But assume it's replacing three separate mice. Recommend waiting for a sale if you are unsure.

Highly recommended! I'd give it a 4.5 If I could, but it's not quite a 5 star.

-Very comfortable shape -Connects very easily, even to Macs -Switches between computers almost instantly -Drivers allow huge amounts of customization -2 side buttons (+1 for connection switching, no macro), 1 side button hidden at the bottom of the thumb rest, scroll wheel left/right/center, gives tons of macro options without making the mouse look full of buttons -Smooth/clicky scroll toggle -Soft touch material on the body is holding up and doesn't get filthy easily -Confident button detent

-May be on the small side for very big hands, but probably still fine -I don't believe the drivers allow custom button combo macros, but still have a huge list of actions available for any button, and can even be program specific -White base may not stay white in especially dirty environments, but mine is still clean -At $80 regular price, if you don't really need the ability to switch between multiple devices all the time, there are better mice at the same price point.

I got this mouse on sale for half price about a month ago and it feels like a steal, super happy with my purchase. Having used the mouse, and knowing how useful the connection switching feature is, I would happily pay full price. If you don't need connection switching it's harder to justify the cost, but still worthwhile in my opinion. Keep in mind this is a productivity oriented mouse, though I still use it for light gaming. Logitech has come a long way in the last 5 years since I bought my one last.