Nope. So far the only positive I've seen is "WELL IT MIGHT NOT KILL FORUM ACTIVITY" which is hardly the greatest reason to implement a tool which can take away the need or desire to use the forum itself.
If you want to build the community then don't give it something which can only create conservations that are entirely exclusive to those online at one single time period. A conversation that goes on in a thread can be accessed and added to by anyone at any time, and that is how new people become integrated into a community, not by giving them a small chance to be part of a chat which might not even happen and won't be recalled by anyone not present anyway.
That principle is extended to the whole forum - it's called spam. As I've written above, a chatbox in which users have to be on at a very specific moment to use cannot possibly hope to contain any meaningful intercourse (lol intercourse) for the community as a whole.
...And then why would users bother with a feature that they can't access all the time? I know I for one would be less than happy to find that partway through an interesting conversation I was cut off because it was no longer deemed an appropriate time for me to be talking - at which point it would probably move to a spam thread, which would then be permanent inclusive for all members, and suddenly I'd wonder why I didn't just go there in the first place, since it's a much better setting for conversation to grow in.

