Hi, I don't know if my impressions are still worth anything coming up this late, but I've picked up the demo and played it for few hours. I'm playing on workstation (etc. machine more than capable of playing a 2D game) and I've gotten consistent slowdows on higher speeds, especially with Bakal's visual effects. Game even crashed on me once, so I've stopped using him, but in general, the speed up option currently leaves a lot to be desired, especially after I got into the mines, the amount of enemies and heroes combined can really cause a lot of stuttering on higher speed, feels like playing The Sims 1 all over again Other than that, it looks good, and is just as fun as before.
Also, another thing, which is entirely subjective, but I have a good reason to say it: I don't like the new cutscene art too much. Azra and Slak is probably the best looking out of all of them (I get a kick from Bakal grinning all the time, I hope that's still WIP), but the most important thing is that the new drawings are not as expressive, they just feel kinda dull. I liked previous art for it's simplicity, but mainly for the amount of personality it had with it's characters reactions. When someone changed their mood, I beleived the drawing, because it depicted it in a nice, cartoonish way, it had a personality. This new art, while more detailed, simply doesn't do that, it feels downplayed, like the artists doesn't know what emotions they want to display. All in all, I might stick with the old cutscenes, I'm glad you're keeping that option in.