I was there:
Lots of fun - I think 80% more fun and 20% a useful tactical tool, it may be more tactically useful on AAS maps though.
Two schools of thought with regard to having seperate Mumble positional teams or combined, meaning you hear the enemy or not.
Lots of banter, congratulations and piss taking going on at the end of round - tactically useless but lots of fun.
For me in a frenetic action packed map quite tricky to deal with it all WELL, but if the servers are a little quieter excellent!
Because we all have the same accents makes positional with the enemy diffficult - Imagine an audio filter that puts on an arabic accent for the insrgents....

Took me a while to get on the correct team SL channel ... we were only two on.
Now if possible I would prefer a server with the most Mumble players on it!
Any idea why Mumble is forbidden on the UKWF server now, I can't imagine the crash was anything too do with Mumble?