Proprietary Vent has a feature that allows you to create PTT binds, separate from the standard one, that sends audio only to the users you specify in its setting.  For example, the channel is populated with User1 through User7.  I set my right shift key to speak with User2 and User4, only. Hitting standard PTT allows everyone to hear me, but hitting right shift allows me to talk with User2 and User4 and no one else.  And the audio is able to cross channels.

I realize this is a feature not utilized by a lot of people, but the group I use vent with uses it often, either to discuss something in private or to quickly speak with someone in a separate channel.  Not being able to speak back in this fashion is something I feel like I'm definitely missing.

Great work, by the way.  Keep it up!