The biggest hurdle is usually that they have to install an IRC client if they're not using IRC already - which in general is very advisable to get in touch with others, be it for development, support or leisure. On the other hand, that's a boon, too, because everybody can pick the client that HE likes.
I'm with the crowd that says that Flash is an abomination which never should play the role for things like online videos etc. like it does today. Die die die! Unfortunately, there are no real easy to setup alternatives at the moment.
Re: New Feature: FlashChat
Come to 
Visit my 
Threaded Mode