I actually have held off on writing about Firefly despite having had an account and actually tried it when I first started this blog back in December.
The reason I held off is I have been pretty much focusing on SIP as the protocol that I've been covering. Rather than being accused of being narrow minded, I decided to open my mind (or really admit that it's more open than some would assume :-) ) But their growth is starting to mean its worthy of recognition and commentary.
Firefly is gaining users, much the same way as Skype or SipPhone, it offers free on Net calls, plus some services like Voice Mail and IM.
So while it does a lot of what the IM tools already do, the addition of retrievable voice mail is something that means people can get past email as their primary means of communicating with fellow netizens easily and maintain an ongoing, non real time "conversation." This means, in the word of the King, "a little less conversation, a little more action."
It's also another way to "STAY CONNECTED."