This is about the Surface Book, not the Pro. They are very different beasts.
I purchased a Book -- the revised model, though they're very hard to tell apart -- late last year. I'm technically on my third model, and trying to return it to Microsoft right now. It's a solid system, just not worth the high price tag.
On the whole, there's almost nothing about it that is irritating. Everything works really well together, and you get a system with no bloatware -- but you can find that in other Signature Edition systems. There's little about this system that is particularly good, it's mostly that everything just works really well together. I don't use the removable screen much, but when I do, it's surprisingly easy to do, and actually verges into "delightful" territory. I especially like that I technically have all my data on my "tablet", so to speak.
There is one particularly nice thing that I'd like to see more manufacturers tackle: there's a USB port on the AC/DC converter. So I can charge my laptop and a phone at the same time, without using one of the two USB ports. (It also has an SD card slot, which I happen to like, but they're falling out of favour.)
So why am I looking to return it?
The hinge is a mild irritant. The way the power cord is run means it gets caught under the hinge frequently, and the hinge itself leads to a fair bit of wobble in the position of the screen; it can be difficult finding the right angle. As well, that hinge means that the screen only tilts back so far, which makes the system somewhat difficult to use when you're standing up.
But what really gets me is that of the three units I've had, one had memory issues, and two have a fairly loud buzzing sound when using headphones -- as in, it's actively distracting whenever listening to something. When gaming, it makes it sound like there's something big happening; when listening to music, it's just a constant distraction. Curiously, this buzzing happens no matter what type of headphones I use, even Bluetooth, so the problem is deeper in the system, not in the wiring of the jack.
Because it's been longer than 30 days, I'm strictly speaking not eligible to return the device, so my hopes aren't high that I can return it. And if the system were not $4k, I could deal with this by using a USB-connected audio device. But for the price tag associated with this thing, I have much higher expectations.
The Surface Pro 4 looks much more reasonable in terms of price. I know a few people who have them, and they all love them -- none of them have complained about any hardware issues. At this point, however, I'd probably wait for the Pro 5; even as a hardware refresh, it's worth waiting the few months it should take for it to hit market.