The Surface Pro (3/4) is one of the most popular devices. It has a large number of things going for it (listed at the bottom of this post).
One device to replace laptop and tablet
Light and portable
Superb stylus, handwriting recognition, touchscreen
High resolution, brilliant screen
Terrific practical integration of software to get work done - browser, pdf, word processing, note aking
The Very innovative kickstand that lets you angle the screen at any angle and still provides excellent support.
Type cover that is light, responsive, with a glass trackpad that has the right size, friction, accuracy, and responsiveness.
It does have a couple of drawbacks and a big one is its "lapability". This means that there are certain situations where it is difficult to find a stable way to position the Surface Pro. I personally have never had a big issue with this but I can see why people would complain. The other limitation is that the type cover's magnetic attachment to the device is not strong enough to support the weight of the Surface Pro and thus you cannot hold it just by the keyboard like another laptop.
I was very excited to see the Brydge 12.3 bluetooth keyboard come out for the SP3 and 4.
I got it last week and while it was terrific in many ways - which have been outlined on Reddit by @prjkthack, it too has one huge problem.
The keyboard holds the SP4 by two "claws" which are covered by silicone shims to prevent scratches. The hinge is quite firm in order to support the weight of the SP4 at any angle. The problem is that when closing the SP4 all the pressure to rotate the hinge falls on the 2 points where the shims hold the screen. This causes distortion of the touchscreen. You can see this in the video above where in the lower left corner of the screen where you see yellowish vertical bands of pressure. I had a friend try this out with another SP4, changed the shims and tried it with an SP3 and it still caused the same problem. I wonder if anyone else is noticing a similar problem.
I am not sure what the long term implications of this pressure would be on the incredibly beautiful touchscreen but I am not willing to test it out.
Also as others have commented, the trackpad is not as good as the glass trackpad of the type cover - it is less responsive, the left click does not work very well and selecting a line of text is not accurate.
I tend to use the SP4 a lot in the tablet mode as I read and annotate PDFs or make storyboards for presentations in PowerPorint by writing on blank slides. For this, it is remarkably easy to just flip the type cover back under the SP4 and it immediately converts to tablet mode. With the Brydge, it is definitely more involved to take the device out of the claws and you still need to convert to tablet mode manually.
Obviously, there are folks who use the SP4 almost entirely in laptop mode and this last point may not apply to them. For me, these issues combined with the increased weight makes this Buetooth keyboard less than ideal. It is possible that with more extended use, I would get used to it but the pressure distortion of the screen scares me too much to try this for that long.