I belong to a couple of groups that have been experimenting with hybrid meetings.  These are just some of my observations.

1)  Sound is critical.  If the speaker is going to be more than 2 - 4  feet from the "computer" some kind of remote mic system may be needed.  ONLY ONE mic can be live at the same time or the "echo" factor makes it impossible to understand what is being said.  Also the more mic's that are on, the more background noise you pick up.

2)  Do you need live audience participation or just the speaker or panel?  If the latter, the "webinar" format works better than the "meeting" format.  You can still allow questions, but they will need to be written via the Q&A or Chat window. But since only the speaker (panel) can have live mic's it limits the audio confusion.

3)  If you are using the meeting format (you want to mix live and online participants) some form of large screen will probably be a necessity.

I am sure as we move along there will be many MORE issues!!  

Hybrid is working quite well for a small group meeting I participate in with 2 - 5 in-person and 3 or 4 online. 

We are still struggling in my Sunday School class which can have as many as 20+ in person and right now has about 6 - 8 online.  We have been using 2 computers in the room for cameras (no "wide angle" lens) and one for sound.  Biggest problem is that we need a BIG SCREEN for video so the person who is live can SEE who is online and wanting to speak!!!

PLEASE continue this discussion!!