Fast forward and rewind on my spectrum remote have stopped working in the latest beta for me.
Tested the buttons on the Apple TV+ app and they still worked, but not in channels (live tv or local content)
Not sure if this affects other remotes or just the spectrum.
What speakers for audio?
HomePods 
Not a huge deal if that’s one of the quirks of the new driver working as good as it is!
90% of other apps don’t use those buttons anyway - and the right and left buttons do the same function when held.
Please try the Experimental audio driver with TestFlight v2024.02.26.2233
Playback is improved with the experimental driver, don’t need to skip forward 10seconds to start audio playback and FF/RW buttons work. Though PiP seems to pause the video and require a skip forward once out of PiP to start.
The Deafult driver(new name for Lab?) actually seems to be working better. FF/RW buttons work, no frame drops, only a slight audio delay when starting video and no need to skip forward.
Pip is silent(not sure if intentional) but coming out of PiP, audio resumes on its own. 
Will update with any other info as I use the drivers.
@tmm1
Not sure if anything was changed in the latest beta, but noticed the default driver now doesn’t work the the FF/RW buttons.
Will do some fiddling and testing and edit this post with any other changes I find with all the different drivers.
Edit: swapping audio driver and then swapping back to default seems to have fixed the issue.
It only works with the Experimental driver.
The app needs to be restarted after switching back from Experimental to Default.