I just found the other thread where tinypoodle and you are talking about it: should I be commenting over there? Will move over if you say so. Anyway:
Alas, my needs are modest, and I neglected to test exhaustively.
No, it will
not forbid multiple instances. The .flit.pid file is created, and the process id is correctly updated if I exit and restart several times, but it will happily put multiple instances all over the place, even without the -m switch. Meanwhile the -c option works fine without the -m option, so I can populate my desktop with multiple flits as I like.
I am using a Rockwell Riptide sound controller, and volume control responds OK, although controlling how much up or down is inexact, and alsamixer is easier and more precise. But the instant mute is very cool.
By the way, if I'm reading the Help file, the clock stops running (the flit clock, not the actual system clock). Strangely, it doesn't always readjust when I close the Help, but will sometimes simply pick up where it left off, leaving me with a discrepancy. I fix it by exiting and restarting. Can't reproduce on command, though, but it's happened three times. Weird.
I
am on a lower system/version than the system reqs in the first post, though: Micro 2.10 w/ Xorg 7.4. Don't know if that would affect anything...
I have noticed something after reading that other thread:
When running new instances, the content appears to be overwritten with PID of most recent instance.
After exiting the most recent of multiple instance, it's (no longer existing) PID would remain in the file.
This is not my experience, interestingly. It's true that the .flit.pid file gets overwritten with the pid of the most recent instance, but in my case, exiting from
any instance deletes the .flit.pid file altogether, leaving the other instance(s) running with no .flit.pid file.
In that other thread, I'm also seeing a lot of commentary about the docking feature, so I suppose I ought to clarify for your sake: I don't use a panel, so I don't have a real tray for docking. What I'm happy about is that the --dock option forces "always on top", which the older extension lacked.