Bluetooth Mice go into a 'sleep' mode to save battery, this will cause about a one second lag
on the first click or move as the Mouse 'wakes-up'.
What Logitech is doing, is to have this 'sleep' mode entered after five seconds of inactivity.
I have a Bluetooth IntelliMouse and it is set to enter the 'sleep' mode after eight minutes
(480 seconds) of inactivity, so this 'lag' is never noticed in any normal use.
This is not too hard on the batteries (2 x AA) as I have been getting eight weeks on cheapest
(44¢ a pair) AA's and just loaded NiMH rechargables to test their life.
Size would be similar to MX900 and has buttons four and five that smaller mice don't.
Unlike the MX900, it needs no "Charging, Bluetooth, USB & AC Powered Console",
it comes with a MS Bluetooth v2 USB 'Dongle', but it was plug 'n play with my internal Bluetooth.
Weight is 160gm (5.5oz) with two batteries (runs fine on one) and ergonomic shape is very
comfortable for your Right Hand.
Speed and accuracy would be excellent for gaming or any other use.
Mouse Wheel is "Smooth Scroll" (no detents or clicks) and this bothers some gamers and it is
one of the features I prefer.