When in windowed mode (not full screen), and the window has the focus and the mouse over the window, please add an option to grab the keyboard input (for ALT-TAB within the remote session, not on the host).

As example, this is implemented in xFreeRDP and properitary Microsoft Terminal Server Client (just as an example, i do not use Windows) and is very very useful.

I'm using XFCE4 on Arch Linux (server and client)