I’ve never tried one but I think it would be awesome to move with a thumb stick and aim with the mouse in an FPS, kinda reminds me of the wiimote+nunchuck combo.

Works great for MMOs where you can keep your keybinds close and free up fingers.

I use the Logitech G13 and it works great.

With the ability to change the UI on the screen I can put the icons in the same configuration as the physical buttons which helped speed up learning what is where.