Can we get a comment from @MICROSOFT please? This issue is all over the internet.
The problem is related to the way the trackpad device reacts to battery performance/efficiency settings.
Microsoft claims this device is best-in-class... this is a great opportunity to prove it.
I'm now suspecting that these issues are related to the Meltdown and Spectre mitigations. Mine seems to be better after I turned them off, and looking back it does seem like they started after the patch and firmware update. So, I'm hopeful that once Microsoft gets a handle on resolving Meltdown and Spectre without killing the machine's performance, we'll be in better shape.
But it would sure help if Microsoft would let us know what's up. If it's NOT Meltdown/Spectre causing this, then it's absolutely unacceptable performance from a $3000+ notebook.
Okay, I did some additional testing and I'm taking back what I wrote above. I hadn't been using my SB2 15" on battery life (mine was lagging when plugged in), and it's just as bad as it was before I turned off the mitigations. At times, it's almost unusable.