Logitech hasn't fixed the typing lag on Mac when using their unifying device if you have a 2.4ghz wireless network or use usb 3.0. Either of those things can still cause interference/lag when typing to the point you'll want to switch to any other keyboard. It's a shame since this has been a long standing issue with Macs and Logitech (3+ years now).
If you use bluetooth the lag is better to the point when it's good enough, but still not as good as a usb keyboard.
Bluetooth however doesn't work for me on the Windows side (Windows 10) as it paired once (after many tries) and then never paired again. So this thing needs some work yet both on Mac and Windows, and for the price point this just isn't acceptable.