On one hand there's Windows' horrid display scaling issues. Hooking the Surface Book into an external HD monitor means dealing with blurry fonts and inconsistant scaling on some apps. Not entirely Microsoft's fault but its still a concern.
On the other, I really like marking up documents and drawing sketches on the screen. The machine is fairly solid and a joy to type on and use on a day-to-day basis.
Like others have said, the trackpad has taken some getting used to. It feels less "solid" than my 2011 MBP's, and it's definitely more limited than the MBP's. It doesn't handle palm rejection as well as I'd like, and the swipe to go back gesture is inconsistent across applications.
There are other issues too. Flux fucks with things; when I use it things get sluggish as the screen begins to warm. I've recently gone ahead and uninstalled it. Sometimes when I press the Windows key to bring up the Start search the search bar doesn't register the keyboard. Detaching and reattaching sometimes confuses the machine and it doesn't know whether to drop into tablet mode or return to desktop mode.
Despite that, if someone reads this in the future, I will say I overall enjoy the machine. I really like what Microsoft is trying to do in terms of bridging the gap between devices like tablets and traditional PCs. My girlfriend and I both like doodling on it, it plays older games good enough with its dGPU, and it's battery life is superb. So I'd recommend it as a great prosumer device.