If there's one thing that'd give me pause over going with an SB, it'd be the rather short battery life of the tablet portion. Granted, that not it's primary use, so it can get away with it somewhat, but the estimated 2 1/2 - 3 hour lifespan is just a little too short if I want to do something like binge on some movies, or get into a book.
This is something I hope will be expanded upon with the inevitable SB2. If they could eek 4-5 hours out of it, I'd be thrilled.
I would have gone with a SB over a SP4 if it wasn't for the terrible battery life of the tablet portion of the SB, and also it has no kickstand. I'm a bit surprised MS didn't allow for this, but then I guess they really wanted to differentiate the 2 products. I'm still waiting for a larger surface pro since I don't really carry it around anywhere, I usually use my 8" tablet for travel. I'd be first in line for a 15" surface pro.