Nice! I like the saturation a whole lot better than the quick-and-dirty tanh~ that I was using. A few quick thoughts...
-You'll want to test the friction control with the Arc. The reason it was kind of hacky is that the friction is displayed on the Arc itself (i.e. you'll see the speed control sink back to 0). I was having a difficult time coming up with a solution that kept the Arc within useful boundaries, updated smoothly, and displayed properly... This current method sounds nicer, but it's not interacting with the Arc. The "line" method stinks, though, I agree hahah.
-When friction == 0, it should just stay at the current speed. I've been using this for more sustained loops and finding ideal spots to scrub. It's also really nice when using the alternate Stretch mode.
-Wow/Flutter should have a depth control. Just a 0-1 that multiplies the W/F jitter at the last stage.
-Likewise, Random Filter/Volume/Compression should be optional.
-Which popup thing was killing you in BEAP? I typically use it with "autoname" enabled, which generates soundfiles in the arcTape directory automatically whenever you hit record. In my mind, that allowed for more rapid experimentation without breaking flow. The sfrecord~ can also give false security. If you hit "Record" without hitting "open" and naming a file first, it will silently post an error to the Max window. That's more of a workflow thing, though. If you like to generate one big, specifically named file, sfrecord~ interferes less. If you like to generate a bunch of smaller files all at once, BEAP's autoname is easier.
I guess, in general, I had started this as an HC-TT emulator, and then it kind of became a more general purpose arc-based soundfile manipulator as I started using it. We could do:
1) Split this into two related projects. One could be a more dedicated HC-TT emulator, with all of the tape and friction features always-enabled.
2) Merge the two projects, but add in switches and controls to determine exactly how tape-tastic the output is.
What OS is your Mac Mini on? There are some required methods for fixing the FTDI driver that have been posted on the updated installation instructions: http://monome.org/docs/setup/
I had to:
1) Reinstall the FTDI driver.
2) Restart to get the serialosc service running.