I'm only 20 minutes in, but I can already tell you that you won't be disappointed. I feel like after just about a third of the video I already fully understand the physical and logical disk format. Like the previous videos, it's chock full of dense information presented with very clear visualization.

Does a high quality version of the Ultimate C64 Talk exist somewhere? I only see fairly low bitrate versions of it. (The embed on Michael's website is dancing postage stamp-sized.)

I'm not sure there is one. There are some mirrors[0] that have a copy of the original recording[1], but apparently still very low-res.

[0]: https://events.ccc.de/congress/2008/wiki/Conference_Recordin...

[1]: http://ftp-stud.hs-esslingen.de/Mirrors/CCC/25C3/video_h264_...

Not exactly what you're asking for, but https://www.youtube.com/watch?v=ZsRRCnque2E while being 480p and rather noisy, was very sufficient for me to watch and enjoy the talk back in the day. The presented material does not suffer much on the relatively low resolution.