I've been looking hard at the Logitech K811 Easy Switch as well. I like the aluminum and black they went with (when is Apple going to switch out the anachronistic white keycaps on their BT keyboard?), the backlight and I absolutely love the idea of a switch to easily swap between computers, but there are a couple things that have me a little hung up.
First, how do the keys feel? From looking at the pictures, they look a little small. Or is that because of the way they rounded out the corners on the keycaps? Do they keys have some concavity or are they completely flat?
Battery. I don't like the idea of rechargeable, non-swappable batteries. AAs will be around forever. In 3 years time, will this keyboard still be functional or will it be gathering dust somewhere because the battery doesn't hold a charge anymore?
For reference, the Logitech K811 here in Korea with Korean lettering is roughly $135, the Apple Wireless is roughly $85.