Yet apparently not business accounts. You can use the integrated hangouts in gmail, and the phone apps, but hangouts.google.com says it's not an enabled app for your account, and I can't seem to find where it's available to enable/add in the admin console (that is, I can find where to enable and add apps, but it isn't listed, and I'm a super admin). The Apps marketplace has third party apps, but that's not what I'm looking for.

I'm able to use hangouts.google.com in both my personal Google Apps domain and my work's Google Apps domain. Almost certainly a setting buried somewhere deep in the Admin Console. :(

Thanks for the heads up. Not that I know it's at least possible, I'll spend some time and did a little deeper. I'm interested in seeing how it compares to Slack (basically, how well it uses the defined groups and membership in them that are already configured).

Non-existent... at least in my experience with my Google Apps account.

hangouts.google.com is enabled on my business account. I didn't enable it, so I can't tell you how it was done. Only that it's possible.