So I've used a MacBook pro/pro retina/air (15" and 13" - switches in that order over the years aswell), and when the Surface 3 came out I decided to give it a try. It was a really odd change for me, I never even tried Windows 7 before let alone Windows 8 or 8.1. I've used the Surface 3 since a day after it was released up until this past Monday.
The first issue for me was the screen size. Now I know 11" screens are pretty popular for mobile people, but for me never dropping below 13.3" to a 12" screen was a huge difference to adjust to. Since then, I had come to get used to it, but it wasn't a change I enjoyed much.
The second issue was the keyboard/trackpad. The trackpad is wide enough, but it isn't long enough. Moving files, selecting text, and moving far across the screen was much more annoying. I haven't bothered using a real mouse in years but found myself quickly trying out a few different ones I picked up at Best Buy.
The keyboard buttons themselves weren't a problem, it was the keyboard not giving the screen support for lap use. I spend a large amount of my time working in bed rather than at a desk or being out, and let me just say that getting and staying comfortable in bed when the screen's stand has to use the bed to stay standing is a pain. That same reason completely prevents you from certain angles too, such as if you need the screen pointing straight up or even slightly angled down (in bed, the only screen angle is up).
As a tablet though, it's great. It's actually quite light, and you'd have to check the specs online but I'm pretty sure it's about 0.36" wide, which is near half that of a MacBook Air. The pen input is really nice, and so is the palm rejection when using it (if the pen is close enough to the screen, it blocks your palm from interfering if it's touching the screen). The kickstand makes tablet work easier too for desk or lap work. You can use the stand to get the perfect angle for writing or drawing (such as an ever so slight angle upward from being flat).
The Surface 3 is a nice device, but they're advertising it in the wrong way in my opinion. They should be advertising it as the advanced tablet (since it runs a full blown PC OS) that can be turned into a portable desktop (to get to the point that the surface, even with the new kickstand, still is best used on a hard surface).
As I mentioned I stopped using it, but I've grown to actually like Windows 8.1 (missed the Mac dock though and downloaded a Windows version for quick application access, it's called ObjectDock and works great for nearly replicating it from open apps to quick apps). I switched to a Lenovo yoga pro 2, and in the last few days absolutely love it. The yoga is best described as a laptop with the option to be used to a lap or desk tablet (you wouldn't use this in the palm while moving/standing, your forearm maybe though).
Anyway, the yoga pro 2 is around 0.60" thick (about that of a MacBook air), ever so slightly heavier (if I remember right not even by a quarter of a lb, though it's lighter than my either 2012 or 2013 air). The screen doesn't detach, it rotates as far as you want it to go, all the way up to the point that it lays flat against the keyboard, essentially making it a 13.3" "tablet." The keyboard and folding screen actually act together creating a kickstand like effect the surface has for touchscreen mode, while still keeping the normal laptop control when you fold it back. The biggest drawback (thankfully I have no real use for) is no stylus support, which means if you get a stylus made for something such as an iPad online, you have to watch your palm because it will impact the stylus if they both touch.
What I'm watching for now is Intel's Broadwell chips. Assuming the fanless compatible chips can compete with i3s (or more preferably i5s as I imagine i7 at the least will still be better than this particular upcoming Broadwell chip), I could see Lenovo using this fanless design to create a yoga 3 at the same thickness and weight as the Surface 3. That with Windows 9 (looking likely at a 2015 release) to return the start menu and change some other less liked features of Windows 8, I think could actually bring some competition to this laptop/tablet in one some better competition. Of course, this all depends on future releases and also in this case a thin and light weight 13" laptop/tablet, where some people have no interest in a tablet that isn't 8"-10".
Just some thoughts of mine and my experience with OSX, Window 8, MacBook Pros and Airs, and now recently the Surface Pro 3 and Also Lenovo Yoga Pro 2.
) and a custom built desktop workstation with a Core i7-3770K and a GeForce GTX 660Ti. I'm in the process of building a cute little #! (linux distro) machine with a Pentium Anniversary Edition G3258 and possibly a GeForce GTX 750Ti. 
