It's certainly high up my list. I'm looking at replacing my Surface Pro 4 and it's certainly a tempting option. It's great that it will work with my Surface Docks, love the portability and the battery life.
I currently take my Surface Pro 4 everywhere with me and take it out to use pretty much anywhere. So having a light device with good battery life and quick turn on is most important. Unfortunately the issue I have with the Surface Pro 4 is the stability with the Type Cover just about anywhere other than a table of flat surface. Try using the Surface Pro 4 on a train or a bus or sitting on the bed or on your knee while watching TV and it falls over and get's really uncomfortable.
Sure in these situations I can just switch it over to Tablet mode, but typing is a pain and doing things like remote desktop to other PC's is just about unusable. I love the Tablet mode for Content Consumption, but it's just not useful for productivity things.
The Laptop design really excels in these portable situations. It has no issues with sitting on laps, beds or being used on trains, buses or cars. It's stable and useful. It still has a touch screen, still has pen support (although not as useful as having it flat, but still there), has much better battery life (according to Microsoft), and a great looking screen. The loss of a MicroSD card slot is a bit of a pain, but not the end of the world.
I have no issue with it only having USB-A. As others have said, the majority of devices are currently USB-A anyway (unless you have been out and spent a bunch of cash on replacing them with USB-C), and you can buy a small adapter which will convert USB-A to USB-C for any you have. I already have a bunch of MiniDP adapters, a couple of Surface docks and a bunch of Surface power adapters so I think it's great that I need to buy no new adapters or plugs. I have plenty of power around and the Surface Power bricks are small and light, so no issue carting them around.
The only downsides I can see with the it not having USB-C is not being able to use a portable battery pack for charging it while out and about. But with it's battery life it's not going to be so much of an issue.
And I am use people will be going 'Why not go a Dell XPS 13/15'. Well, there are a few reasons. I will be going the top of the range i7 16Gb memory version, so the price difference between the XPS 13 and Surface Book is around $600AUD. My issues with the XPS 13 are the keyboard (I just HATE typing on it. It is not good at all for me), the trackpad (The Surface trackpads kill it), the battery life, screen (while the screen on the XPS 13 is good, the Surface screens are better), and lack of pen support.
Sure we are going to have wait and see what happens with real life battery stats to see how the Surface Laptop does stack up, but the keyboard, trackpad and speakers on the XPS 13 are enough to kill it for me.
The XPS 15 is well and truly out as it is much bigger, meaning much more of a pain to cart around, and still has the same keyboard and trackpad feel.
So all up, yeah I will probably get a Surface Laptop. My Tablet needs are now met by the Samsung Galaxy Tab S3, so what I do need is a stable portable laptop. My Surface Pro 4 is, sadly, too unstable in portable use in many situations. The Laptop form factor will work far better for me and what I need.