Mattermost

Comments: Mattermost allows us to quickly keep connected to our colleagues across the world. It allows people to form groups and chat easily to many different teams, all within the same desktop app, web app, or mobile app.

Pros: This software is very easy to install and supports a simple Docker install, which makes it easy to keep up to date and secure. There are multiple examples on installing and running Mattermost in different cloud hosting environments, and the user community is also very helpful.
Running the software locally means you can keep a much better eye on its security and usage.
Its user management and directory integration is superior to Slack's.
The desktop and mobile clients are fast and easy to install/configure/maintain.

Cons: There's not much that I dislike about Mattermost. Its open source nature may put some people off, but paid support and enterprise licensing solve that issue immediately.

Comments: A platform to discuss issues and feature ideas around our open source project, without cluttering up the threads on github. A great way to stay in touch with devs from all around the world.

Pros: That we can host it ourselves, for one. We used to use the free tier of slack, but quickly discovered that the message limit was causing issues when we needed to recall conversations had in the past. It's been relatively hassle-free in getting it set up, and the whole team love it! One or two of us (myself included) were inspired to brush up on some of our coding skills when we discovered it didn't quite have the integrations that slack did, and as such have learned a lot about how Mattermost is put together, and how to create bots to get the information we need via webhooks. The Mattermost developers and community at large have been very helpful in answering questions when we've come up against issues, and I have even got a couple of my integrations featured on the integrations page of their website!

Cons: Really, not a whole lot. Ideally I would like to be able to sign into multiple slack servers from the mobile app (though, the native app has really come along in leaps and bounds recently). The only thing I miss from the Slack days is a sidebar/widget that tells you the local times of the other users (handy when working with folk from overseas!), though we have recently developed our own slash command to return this information, it would be nice if it was built in to the server. I should probably feed this back to the devs.... ;)

Comments: We solve the need to have a Support/Chat/Client support software, with this we have it all in one.
It helped us keep communications across teams and countries painless.
Integrated with all entire ecosystem from Taiga.io to Gitlab for a better DevOps experience.
Overall every chance we had to contribute we toke it, thats why we decided to fully translate mattermost in Romanian language, do we did.
If you need a centralized devops collaborative platform, give it a try!

Pros: One executable binary, simple to upgrade and maintain!
Reliable self hosted alternative to other SaaS PaaS options.
Cross-platform applications ready to use.
Amazing open source community built around the product, friendly and helpful people!

Cons: It requires integration directory to allow users app deployment in mattermost ecosystem with ease.
A bot repository is missing, this can fir next to all others apps and allow users automatic deployments of any apps from the store.
Store idea is not a new concept, and a company that respects themselves should make use of own repository.
Allow users to safely deploy tested and 100% working apps along their Mattermost instance.

Comments: Control over our hosting and data

Pros: Open source and self hosted, I don't get irritated if slack goes down and I don't have to worry about my data security or my data just being lost of the company goes belly up. This is far and away our primary reason for using this instead of Slack,Hipchat,Cisco, etc. It doesn't ask anywhere on this survey, but we use it for about 80 people, 60 staff and then various clients and contractors. We don't use many of the enterprise features, we just pay the licensing to support open source.

Cons: iOS and Android Apps are pretty idiocy, they're getting a bit better, but they are easily the worst part and I field lots of complaints about them. I would trade all new features and other fixes for faster and more reliable apps. The web interface is much better, but a bit buggy, nothing serious but little lags and quirks persist longer than I would expect. The install process is also a bit silly, copy pasting files and such, a provided .deb or a custom apt repository would be 100x better and save me upgrade time and downtime. The lack of this is surprising considering almost all other software I use has this, even when it is free or small.

Comments: Between communications platforms, voice calls, emails, and texting, there are numerous ways to communicate with colleagues. My company decided to use Mattermost because it helps us avoid clogging up email when we have quick questions to ask or non-essential company-wide messages to send.

Pros: My company has over 200 employees ranging multiple departments (from editorial to strategy to support) and offices. Mattermost helps us stay connected in a quick and efficient way because we can easily connect and disconnect from channels according to our business or personal needs. For example, I am part of a group that connects members of my immediate editorial team and other groups that connect my larger team, my support resources, and strategy team members. It helps me stay organized in my communications, and it's much easier than using email or texting to communicate quickly with people on a daily basis.

Cons: Because my company is relatively large, we have dozens of channels on Mattermost. I sometimes find it difficult to find specific channels that I'm not already a part of, especially if I don't know the precise name of the channel or group. This sometimes ends up being a hindrance to what is typically quick and efficient communication. Nevertheless, I enjoy using Mattermost and would recommend it to other businesses.