I take my Surface Pro 4 to work with me every day. During the day I will use it at meetings, standing up as a clipboard, when giving presentations or any other occasion where I'm not at my desk.
I will use it fairly evenly distributed between laptop (with the type cover), tablet or tablet + pen. During the day, battery life and the ability to switch it on quickly to get things done is crucial. It annoys me when it has gone into hibernate and I have to wait those extra few seconds with people talking at me in a meeting before I can start doing stuff.
When I'm using my work desktop I usually switch the SP4 screen off as I have 3 large monitors on my main machine. That said, there are many days where I will do most or all my work on the Surface Pro 4 because I'm mobile in meetings or at clients.
I will often carry on work on my commuter train so there I will probably have it as a laptop with the type cover. If I'm reading articles, annotating documents or consuming media I will pull the type cover off and use it as a tablet.
When I get home I will plug it in to the dock where I have external peripherals and use it as a desktop when working from home. I keep the device's screen on and use it to keep Outlook and/or OneNote open whilst I work with my main applications on the bigger screen(s).
When work is done and it is time to play I will more often than not unplug the device and use as a laptop or tablet on the sofa.
For me, knowing that my battery has enough juice to keep me going through all my activities is crucial. I dream of a day when battery life anxiety is not part of my routine anymore.