Just upgraded to Sierra & Blender 2.78, mid-2012 MacBook Pro with GeForce GT 650M.

Trackpad pan / zoom / rotate works fluid for me, with or without Continuous Grab.

Also fluid when using Intel HD 4000 on same system. With or without Continuous Grab.

This is the first report I've seen about regular trackpad problems. Do you have a Wacom plugged in? Those don't get along with Continuous Grab.

Sorry I wasn't too clear on that. I'm using a regular mouse. This happens on MMB+Drag in the viewport. The trackpad works fine. But I guess that won't trigger continuous grab. Trackpad gestures seem not to be the same as MMB+Drag. But I'm just guessing here...

Actually issue occurs whenever continuous grab is applied (scale, rotate, grab, ...). Trackpad works fine, wired mouse not. Interesting is, that when I use the very same mouse via bluetooth, it works correctly.

System information:
macOS 10.12.2
MacBook Pro (Retina, 13-inch, Early 2015)
Intel Isir Graphics 6100

Blender version: 2.77

I can confirm this issue. When continuous grab is enabled, rotate, pan and zoom behaves erratically. Once it's disabled, it's smooth again.

System information:
macOS 10.12.5
Nvidia Titan X (Pascal)
Mouse: Razer Ouroboros (wired)

Blender version: 2.78c

I can kind of reproduce this, when working in a heavy scene. In that cases the mouse cursor only moves when Blender redraws, and feels quite jumpy, though I'm not sure if it's what's being described in this ticket. Sometimes the mouse position goes out of sync with object being dragged.

Looking at the code, one possible issue is that we are both getting/setting the current mouse location, as well as handling queued up events. With a high frequency gaming mouse we might get more events in the queue lagging behind the current position, leading to mismatches. The same could happen with a heavy scene and slow redraws.

I made a quick screen capture on this: link to youtube

I could test it with a gaming mouse now and the issue is much worse then. I found a fix now, mouse motion should be always smooth now, both for gaming mouse and heavy scenes and other mouse.