Yep, this was a great way of separating streams. The only problem I occasionally hit was that if a channel didn't exist it didn't change whether a hashtag went to a 'channel' or not... it went to a non-existent channel instead. So a message like "#Goodbye Jaiku" (a hashtag required by one of the backup services) went to a #goodbye channel, and didn't get picked up by their backup script easily.
It would certainly be nice to be able to have 'multiple streams' in +Google+
but it's going to be a tricky thing to implement with the same hashtag notation without a lot of confusion. Maybe a slightly different character, or a double character? like ##Channel or #!Channel.
It would also be nice if people could see what channels you post to and opt-in to just your
posts for that channel, without having to opt-in to the whole channel... if I post about a conference some people might be interested in what I'm doing, but wouldn't care what others are doing at the same conference.