I've been randomly messing around with Topaz Video AI for a couple years now. It's a neat tool but I have trouble ignoring the typical "tells" of AI upscaled footage (thinking primarily of a waxy look). That's probably on me for not tweaking the settings enough, although I've noticed the same thing about upscales from other people.
I have a lot of DVDs that I've ripped and deinterlaced with QTGMC. Every time I try upscaling them I end up preferring the look of the non-upscaled version. I think I will always prefer a high quality source at its native resolution over an AI upscale.
I will say that it has the best motion interpolation that I've ever seen. I haven't noticed any motion related artifacts in any of the clips that I've tested.