I personally haven't had time to check any of the stream out yet, been very busy writing. That said, I'll have to check it out sometime.
I'd assume you're going to find a lot more diversity in larger streaming platforms like Twitch and Mixer than Vimm at the moment. How can we promote Vimm to more people?
I think focusing on its strengths and the things it offers that other streaming platforms don't would probably be the best way. For instance, you don't need a Steem account to sign up for Vimm. You could sign up for Vimm first and add a Steem account later, which should make signing up for it easier. That doesn't really need to be advertised, but it's something in its favor.
Also on other platforms you have to jump through a bunch of hoops before you can start earning. You have to have a certain number of followers, you have to have streamed for a certain amount of time, etc. On Vimm, as long as you have a Steem account connected, you can start earning right away. Or at least you could if more people were using it.
Some platforms also have withdrawal minimums before you can actually withdraw your earnings from them, and these are often steep enough to mean whatever earnings you make you can't access until you get bigger and much more popular and start earning a lot more. On Vimm, whatever you make you get. There's no need to withdraw it, whether it's Steem and tokens from upvotes, or Vimm Gems.
All are definitely benefits of Vimm! Is there any way to stream to multiple sites at once?
The technology exists, but while using the basic features of the service Restreamio is free, in order to use a custom RTMP destination, which is needed to also stream to Vimm, you have to use one of their paid packages. I haven't really done the research yet to see if there are any other free alternatives that would work.