In the case of the IRC-like channels (public etc), the fact that you can ask something + close the browser, and when people reply to you buy mentioning your name you get an email follow up with the answer make it an ideal Q/A platform too, not needing to lurk after asking your question or scroll for a while to find if anyone answered you is an immense value.
Don't basically all of the services do that now? Skype doesn't, I know hipchat does.
It's actually influenced my thoughts on how I want to structure one of my own projects. The actually useful free version that as you start using more of the advanced features (but not specific ones) starts costing seems like a good model to get people in and using your product while also incentivizing users to become customers.