Maybe "killer feature" was the wrong way to put it. Matrix has good support for things like bots and bridges, but those bridges are written by people like myself who are mostly just trying to hack something together and make it work. Over time they're becoming more solid and easy to use, and hopefully at some point it will just be a matter of `pacman -S hangouts-bridge` or whatever.
For certain things it's pretty easy. Bridges like IRC, Gitter, and Slack are a couple clicks from within the Riot app, although you do have to go goof around in the settings for those third party services to get it talking to Matrix. There's also starting to be some hosted services for bridging public rooms where you can just invite the bridge bot to the room to get things going. Like here: https://t2bot.io
The thing that I find particularly exciting about Matrix is that it 1) has support for doing that kind of thing, and 2) it can scale pretty gracefully from a 1-to-1 chat all the way up to a room with thousands of users. So you can (even if it isn't always easy, currently) bridge a 1-to-1 Hangouts chat, or a Slack room with a few dozen people, or a Discord server with thousands.
I'm not trying to oversell it right now. Many of the bridges are difficult to set up and not really something the average user will be able to do (although there are many that are). But it's pretty damn cool that we're able to do it, and I expect it to get easier as things progress. Matrix itself is only just now leaving beta, and even then the reference server is slow and still missing some big features. So the "extra" stuff written by the community is going to take a while to develop into "click to enable".
For certain things it's pretty easy. Bridges like IRC, Gitter, and Slack are a couple clicks from within the Riot app, although you do have to go goof around in the settings for those third party services to get it talking to Matrix. There's also starting to be some hosted services for bridging public rooms where you can just invite the bridge bot to the room to get things going. Like here: https://t2bot.io
The thing that I find particularly exciting about Matrix is that it 1) has support for doing that kind of thing, and 2) it can scale pretty gracefully from a 1-to-1 chat all the way up to a room with thousands of users. So you can (even if it isn't always easy, currently) bridge a 1-to-1 Hangouts chat, or a Slack room with a few dozen people, or a Discord server with thousands.
I'm not trying to oversell it right now. Many of the bridges are difficult to set up and not really something the average user will be able to do (although there are many that are). But it's pretty damn cool that we're able to do it, and I expect it to get easier as things progress. Matrix itself is only just now leaving beta, and even then the reference server is slow and still missing some big features. So the "extra" stuff written by the community is going to take a while to develop into "click to enable".