Group chat isn't anything amazing with it but I haven't found it deficient. Maybe I'm using it wrong.
I've recently joined a new company where everybody loves to complain about Skype/Lync stating similar things to this. But I have zero issues, and had near zero issues at my prior company where it was widely used and improved remote working considerably. The only difference I can see is in this new company everybody is using MacOS (and admittedly when I tried it on Mac it was terrible).
The current solution requires persistent rooms to be enabled, a new AD account, and a VM running our proxy.
Once set up though, you can do 2-way, real-time sync between Slack channels and SfB rooms (https://vimeo.com/174265102).