Length of the video is obviously short, for a longer video, would you prefer 1 segment, or separate rounds you can compile into your own playlist?
Why not both? You could include a default playlist file and after a playthrough I could select out the ones that I don't like that much or shuffle it.
How do you think the side beat-meters work?
I liked it already in Corruption 1 by Frivolous. He additionally separated them to left/right as left/right hand which was a pretty good idea imho. But I like your beat-meter visual better, my only problem is that the "balls" are a bit small and sometime lost track of them. If you want to stay with this size you may want to use some kind of color change when a beat change is going to happen.
How do you find the speed and pacing?, too slow/fast, or to long/short acceleration? (Base is 145 and going to 290 in the very end)
For a short video like this it's ok for me. You didn't rushed the first part and there was a nice build of speed in it. Maybe I could enjoy some more slow paced part later as well. Slowing down let the blood back to your shaft so it usually give back / build sensitivity. But I was satisfied with the overall composition of the pace changes.
How do you find the syncing? does it work for you or do you not care for it?
It was really good it adds a nice level of immersion for me. Good job with it.
I missed some longer oral part and I would pushed the introduction of anal a bit further (again to build up some tension) but all-in-all it's a very nice job and I really enjoyed it. Also I really liked the 10-20 minutes category and it's a really shame that there is not that much of it out there. So thank you for your work I really appreciate it!