Where I work, it turns out the Surface Pro 4 got chosen as the de-facto standard issue PC for all new hires, moving forward, unless they request a Mac instead. (We're a shop with about a 50/50 Mac and Windows PC mix. Lots of creative types work for us and often feel more comfortable or confident working on a Mac, so we give them that option. Other groups like Finance require Windows for the accounting software we run.)
Our whole I.T. group was issued Surface Pro 4 setups to use first, so we could get a real, hands-on evaluation of them for a while before recommending them to anyone else in the company. My experience is, as long as you don't totally cheap out and buy the lowest-end configurations -- you completely forget you're not on a modern, mid-range performance desktop PC when it's docked with a standard monitor, keyboard and mouse.
When I have to use mine on the go? I dislike the compromises it makes. The pencil stylus works pretty well but it's not that useful for most of what I do. For I.T., I need to remote into serves and make changes or update inventory spreadsheets or respond to emails and help tickets in the web-based system. None of that is made any better with the pencil. So that means using the keyboard cover with it, and that thing stinks. Even if it had better keys and feel, it's also just not pleasant how you have to flip back the plastic kickstand and use the flimsy cover on a flat surface to emulate a traditional hinged notebook. Doesn't work well if you're really trying to use it in your laptop instead of on a table. And the whole unit, with its plastic casing, just feels junky compared to the aluminum used with something like Apple's iPad. Not enough USB ports on a Surface Pro 4 either.
But the thing is? A lot of our employees WILL find the pencil really useful. They use Adobe apps and other drawing packages regularly. And others are more concerned about carrying around the thinnest, lightest-weight machine possible, so they like it too. Even the SP4's power adapter is really small and light compared to the bricks they want you to carry with you with many other machines.
And lastly? Just because MS makes it, they can do the type of integration that has always given Apple the edge over everyone else until now. They can push out firmware updates or driver updates as part of the normal Windows Update process, ensuring it stays current without users having to seek the updates out on a support web page or use clunky 3rd. party updater utilities that are known to screw up.