I've owned most variants of this knife, other than the sprint runs. I like the frn zdp-189 version best. The G10 does feel like a more premium model... until you go to open it. I've had 2 and the action wasn't as nice on either of them as it is on the frn model. So no, I don't think it's worth the uptick in price. I do think the zdp blade is worth the extra though. Spyderco's ZDP is still a contender for the best blade steel available. Love it.
The SS version is a different beast entirely. It's more of a churchgoer sort of thing. It's pinned so you can't adjust blade tension, unless you just squeeze it in a vice, and it will develop play over time. I wouldn't say it's so slippery that it's hard to open, but it certainly doesn't have much traction.
For my money, it's the FRN Zdp-189 model all day long.