The Book's almost what I expected and I liked the focus on the right things (quality of input and output peripherals, form factor innovation) but lets look at the few things that were left wanting:
I think at $1500 the 8 GB, 128 GB look a bit skimpy. (and I mainly say this because it's $2700 to get more than 8 GB RAM!)
Good measures for "skimpyness"
1) is to see how many most bloated AAA games can you install on a new computer with price in $$$$. Answer here is... 1? I'd have started all models at 256.
It may be security related choice to avoid USB 3.1 Type-C but ... ideally this would have had that in a way that you can plug in a PCIe-passthrough device, then have the OS ask the user if they want to enable passthrough before DMA is enabled through that bus... Now the lack of this bus (and perhaps any DMA bus - probably you can't get one through the dock even) makes this a bit suspect in future proofness as high end external NAS, audio solutions, nic etc might want to use 3.1 pci-passthrough in future..
So I am bit concerned this might fall into the "not future proof enough given that price"-niche. Give me $1500 Surface Book with 10+ GB RAM, 256+ GB SSD, USB 3.1 Type-C and a PSU that's not heavy and can handle 1 12V 3.5" hdd attached through 3.1 Type-C and then I'll rush to the shop. for $2000 I'd like to perhaps see mirror/sync dual-SSD option, such that both keyboard and display has own SSD, with the SSD in the keyboard easily removable so if the tablet goes kaput, you can take the SSD from the keyboard and move that C: drive to another computer and keep working while waiting for replacement tablet to arrive.
And lastly. Lets say I got the $2700 model so I had 16 TB as a serious desktop replacement system. 1 year warranty! I build my desktop such that pretty much every part has 3+ year warranty.
At minimum up the warranty to 3 year (otherwise I have to assume this isn't built to last more than 1 year) if this is serious kit worth $2700 and add USB 3.1 Type-C option - some might not want it due to security fears but I do (or some other external PCIe bus that can be toggled - there are relays that could be used for this type of purpose if the bus can't be blocked from the cpu)