I got a Surface Book on launch day (one of the i7s with an nvidia GPU). A rough summary:

Good:

* The build quality is stellar.

* Having the CPU in the screen means the keyboard never gets uncomfortably hot, even when running games. Very comfortable.

* Pretty fast CPU.

* The SSD is obscenely fast, I can get more than 1gb/s on sequential reads. Wish I got that kind of performance in my desktop.

* All the custom hardware integration (the latch, rotation, tablet mode, etc) is pretty robust.

* Good touchpad and pretty decent keyboard.

* Great battery life. When I'm reading ebooks or news I can easily get 5hrs out of the tablet; the laptop mode lasts way longer than that. The numbers in the Anandtech review are pretty representative. Playing Armello on the tablet gets a few hours battery life; I'd probably get 5+ using Steam In-home Streaming.

* When the fan is running (high cpu load, etc) it's very, very quiet. This is the quietest laptop I've ever owned.

* The external port dock is pretty convenient.

* The charging connector is magsafe-style and it's already saved me from a couple nasty incidents.

* You can charge the tablet by itself if you want to.

* The pen and digitizer are great. I have a pretty reasonable time doing web browsing, email and IM on the tablet using the pen to write. The quality of the pressure sensitivity and precision tracking on the pen is pretty good.

* The iGPU is actually (though still only somewhat) up to the challenge of driving the panel at full DPI. Past high-DPI laptops I've owned had Intel GPUs that were clearly not up to the task of compositing the whole screen at 60hz while rendering webpages.

* Considering the problems I've had with the device, Microsoft customer support has been helpful and responsive.

Bad:

* In general the Surface Book and its accessories are just too expensive.

* Intel's video drivers are a goddamn trainwreck. It's an embarrassment. I've had more BSODs (all in the Intel drivers) and TDRs (at least a dozen video driver resets) in the couple weeks I've owned this thing than I've had all year on my desktop. When you're using the NVIDIA GPU in the keyboard things are pretty solid, except that Intel's surface sharing implementation is also totally hosed so vsync doesn't work right. :(

* The WiFi drivers (and probably some other device - I haven't figured out how to profile windows user-mode drivers) are really terrible, they burn a ridiculous amount of CPU and cause latency spikes that make audio hitch. The ethernet in the port dock is fine, at least.

* The cable on the port dock is too short and it's actually quite inconvenient.

* The keyboard/tablet latch requires ever so slightly too much force to remove - It's pretty hard to do one-handed without lifting the whole device. (Very easy with two hands, though.)

* The Fn-lock setup on the keyboard is an annoyance (but not remotely as bad as past Microsoft keyboards with this design)

* Microsoft hosed palm detection for pen input in Win10 and it's a real annoyance. It's not as good as it was in 8.

* The touchpad drivers don't have adjustments for things like palm detection.

* The weight balance between keyboard/tablet is ever so slightly off, such that if you fully extend the screen it tilts backward a little. Not a problem when typing, but it makes me nervous :-)