I haven't picked it up yet, but will at some point. Currently playing through an EU4 campaign, which has a chance of making it to 1820 and might get converted to a Vicky II game, and also started a HOI4 Belgium game, which is not likely to last much longer.
In large part I'm in "wait for the first few patches" mode, which I tend to do for any Paradox expansion or new game. EU4 1.34? Wait for the bug fixes, now it's great. First-version EU4? Pick up at release, play a couple months later. HOI4? I think it was on 1.4 before I picked it up. Now that Vicky III is at 1.06, it's probably fine, but they just put out a teaser for the upcoming 1.1 patch which promises to make things more fine... so maybe that's the right time to pick it up? It does sound like it was generally okay at launch, but I'm not an early adopter in general.
All that said I'm sure I will pick it up relatively soon, and I doubt I'll be going back to Vicky II after I try it, just as I haven't gone back to EU3. I think Vicky II is the one that Johan described as "the UI God forgot", and there's such a huge difference in UI quality between it and CKII. Specifically in the "can I learn to play this game without having the Wiki/manual available all the time?" sense. But Vicky II also does a poor job in general of surfacing information about the economy and politics, so if Vicky III does a halfway-decent or better job at that, it would be really hard to go back. There are so many things I learned only by intuition, cumulative experience, and peering through the fog of Wiki articles in Vicky II.
I'll probably play Prussia or Austria first, I haven't played Austria since AHD, and Prussia is the most major power that I never played all the way through in Vicky II.