I have the i5 256 GB Surface Book w/ 1 GB Nvidia graphics card in the base and I recently started using SketchUp. I noticed after a few days that the fan behind the screen where the CPU is was whirring loudly when I was doing SketchUp. I began to suspect that the graphics card was not being utilized. This was the case as I learned you have to go to Control Panel --> Hardware and Sound --> Nvidia control panel and specify for SketchUp to use the graphics card.
My CPU ran a lot more cool after that adjustment, however there is still some buggyness where sometimes after bringing the laptop out of sleep the computer won’t recognize the graphics card as being installed. One quick way to see this is in the system tray if there’s an icon saying it’s ok to detach the screen, your dedicated graphics is not in use. The fix for the problem is oddly to detach and reattach the screen, but that doesn’t prevent this from happening again.
Regardless of that user-unfriendly problem I am really happy with my Surface Book and feel that its fit and finish and capability is much higher than other PC laptops on the market. The screen is also insanely bright and color-correct, as well as being a 3:2 ratio which is great for productivity.