Yeah, I went with B4 too, definitely "sluggish", but I suspect a lot of that will get fixed, before RTM.
I wonder how much of that is due to a device that was never designed with all the new "doze" features for apps, like the Pixel was, from day 1?
Having dedicated h/w for fast resume and predictive fast loads of a small handful of most-recently-used apps is a lot easier, if you have a lot more horsepower at a given power drain (i.e. 810 vs 820/821 vs 835/836) rate.
In theory, given that the 820 was about 30% more efficient, and the 835 another 20-30% again (obviously amortized), that resume can come at a LOT less power cost.
I really notice this on the ZTE Axon 7 I got for our daughter, it's a heck of a lot quicker on resume than my 6P; I thought my 6P was pretty darn good still, until I set this one up, oops ;-]