Your solution is pretty good, but it has some drawbacks:
1. when you kick the mentor or vendor out of your main room, they no longer have a record of what happened. Since Sameroom replicates messages across channels, everyone has a copy (like with email)
2. If your mentor or vendor wants to involve someone else from their side, it's not easy (they have to ask you to send an invite). With Sameroom they would control access on their end of the discussion.
3. Your invitee is forced to use Slack, which isn't ideal if they normally use another tool, say HipChat. Even if they already use Slack, they have to switch teams, which... well, it doesn't seem to scale very well.
Our goal is to be the plumbing that connects other apps/services. We think the main value here is the possibility to use whatever app/service you like best to communicate with other teams.
When people have great search at their disposal they actually start relying on chat to keep their important assets. This enables nice dynamics--the more history they have over time, the more valuable it gets.
If you quit LeChat, or at any other point in time, you can download full history in plain text and in JSON format, which retains important metadata.
Sure, if you sign up we are sending announcements about new features.
Dev tools integration is our big focus. So far we have GitHub, BitBucket, CloudForge and Airbrake plus raw HTTP and direct email address for each chat room. One of our customers created a Ruby Gem [1].
Our immediate plan is to provide great native apps for mobile and desktop that will use our proprietary protocol. We like to think of LeChat as "Dropbox of chats", you never leave your conversation as you move between desktop, web and mobile devices. Gateways for XMPP and IRC are further down our list and are more on API/integrations side.
Would you be interested in us opening a generic API to apps like yours so we handle all protocol differences?