I own the Ink&Slide, and an iPad Air 2 (which is not the best solution at the moment).
I downloaded the Adonit app, Forge, and actually the Ink is working and fully recognized, although I don't know if they implemented their last SDK in this, because I have noticed that sometimes is still having some problems, like a line it might be discontinued even if you're drawing with no interruptions whatsoever.
I tried the new "Forge" app and the adonit jot pro touch with pixel point pen worked horribly with it! I have an iPad Air 2. Just letting people know.... "the struggle is still real", emphasis mine.
i did buy the ink and slide afterwards. I'm still trying to adjust with using it as it keeps misbehaving during use
I find that the latest version of Forge is working great for me with the Ink. ( The slide does nothing ) In fact, I've switched to Forge completely while Line updated the pen sdk. I think Adonit managed to "fix" the problems with the iPad Air 2 enough. I can now write and draw in forge in ways I can't at all in the adobe apps. At least that means buying ink and slide wasn't a total waste. Here's hoping Adobe apps catch up as well. It's a real bummer, as the software features itself are great.