As an IT guy/consultant, I have supported the Surface Pro 2 forward and the Surface Books and they're well-made products. I don't believe the Surface Books are necessarily worth what they cost, but they're a cool piece of hardware. I like the Surface Pros and do recommend them but I can also fill you in on some of the issues I have seen.
The primary reasons my wife liked the Surface Pro 3 was the size and the tablet/drawing aspects. The size fits very well in her bag without needing its own case and the machine is much sturdier than it looks, feeling very well made. She does a lot of on-screen drawing for her clients (bakery/cake design) and the screen digitizer, made by Wacom, is top notch. That company has forgotten more about tablet digitizers and active pens than any other manufacturer knows at this point.
These products are all trying to battle the Macbook/iPad users so they are working to emulate something like the retina display. My wife found that the default resolution was much finer than she really wanted. The typical HD screen at 1920x1080 is a pretty tight resolution on a 13.3" screen but at 2160x1440 on a 12" screen with her SP3, she had to increase the system's viewing scale for everything and has not always liked that because it can throw off some views and is, at times, a little blurry.
The two guys I supported that had Surface Book 2's had 13.5" screens that were using a resolution of 3000x2000 and had some of the same issues with an added problem. When using remote desktop sessions from the laptop, they were made to emulate the same resolution, making the remote machine interface even harder to see in smaller windows. I had some issues with power adapters for the Surface Books, as well, replacing 3 in a matter of 17 months or so.
My wife originally used the keyboard made for the Surface Pro 3 but had problems with the mouse eventually...I think because of the keyboard flex. We changed her out to the one made for the Surface Pro 4 and it feels like a much better product. Note that when people talk about how difficult it is to keep the alcantara material on the deluxe keyboards clean, they are speaking from experience. Looks and feels damn nice new but gathers dirty easily over time. As others have said, I find the SPs difficult to use on my lap when on the couch or in bed but my wife doesn't mind it. I think she's figured out how it works for her and I haven't used it enough to do the same.
If you aren't planning on separating the screen to use as a standalone tablet, I highly recommend looking at the Lenovo Yogas. You can get as much machine (or more) in a much more affordable package and they are very well made. The best thing I can say is that, as an IT guy of 25 years, it's what I spent my own money on and I have used the Yogas for 3 generations. You can fold the screen all the way over and still use them as a tablet but the keyboard is a hard keyboard that is permanently attached.
I would say that the lack of easy ability to work on these versus a standard laptop or 2-in-1 (which still isn't a cake walk) is a bit worrisome. I know there have been a couple of major issues with the Surface Pro 3 and 4 that have happened to a subset of owners, mostly screen or battery related, but all laptops have some manufacturing problems that pop up. As an example, Lenovo has had a black screen problem occur for many that I've never seen in supporting dozens of the Yogas.