I was in IRC for about a month after I first joined the project, but it was always dead so at some point I stopped bothering.
I think I'll start popping back in.
It seems a little inconsistent that we're a project to build a crazy visionary libertarian utopia and reduce dependence on governments and big corporations, but most of the other developers use Skype on their Macs because "it's more convenient" or somesuch...
I'm pretty inactive on Skype developer and delegate chats too, I'm too busy doing actual work. That, and I am uneasy about running proprietary software on my development machine for a variety of reasons, so I run Skype in a separate user account and hence don't get desktop notifications or anything.
I answer questions and clear up misunderstandings here on the forum and Github, where most of the people are, and I assure you the time expense is
far from minimal
The main reason I prefer forum / Github to chat is that chat is ephemeral, my answers only help people who happen to be logged on at the time. Whereas if I post on the forum or Github, someone can search and find my answers weeks, months or years later -- each answer helps more people and there's less chance of repeats of basic questions.
I'm not a big fan of the Mumble sessions either, for me voice chat is incredibly slow compared to reading, and requires even more immediacy -- if I pop off to the restroom or do an hour of work and check back into IRC afterwards, I can easily catch up on what I missed in a minute or two, whereas that information's simply not available if it's a voice chat. And recordings after the fact are limited use as well -- they can't be searched or skimmed. I'd much prefer transcripts, and I believe at some point there was a bounty to produce them. I don't know if that ever happened or not, I do know I can't remember ever personally reading one.