Nobody likes being scrolljacked. You scroll down the page, and something unexpected happens. The scroll speed is abnormal, the behavior doesn’t map to the action, or some other nastiness takes place.
To me, the worst is when you scroll down a little and an entire new pane of content slides up. It feels so unnatural, as if I’ve lost control of the page.
Good interaction design makes the user feel like they’re in control. It doesn’t change up behaviors, especially default behaviors, just because it “looks cool.”
There’s only one example of effective scrolljacking I’ve seen, and I’m not sure it even qualifies as scrolljacking. On the website for FiftyThree’s Pencil, an image of the pencil fragments into its component pieces as you scroll down. It happens smoothly, respects the rate of scroll, and degrades gracefully. It’s just a graphical frill that enhances, not replaces, the default scrolling behavior. Kudos to Jonnie Hallman for that, and for the explanation he wrote here.
Anyway, respect the user’s choices, and don’t hijack default behaviors unnecessarily. It may look cool, but it’s terrible design.