We use this tool really because we don't have a lot of specific needs for our communication. We don't need Slack, and Google Hangouts is free, right there and integrates with our email.
Google Drive is just easy. It integrates with all of the other Google features we use, and it does everything we need it to do. We occasionally use Dropbox for particularly large files, but Google Drive integrates with so much, we really prefer it.
We just switched over to Namely from ADP. It's got a really nice user interface. We still have ADP as well, which is horrible, but Namely is a great solution for bringing everyone together. Because the interface is so simple, everyone can handle their own needs, like vacation time, without needing to funnel it to someone.
We use Concur for expense reports and travel booking, which is handy. Concur actually has a pretty decent app for capturing receipts while you're traveling and keeps everything organized. The one downside is that the interface for booking is not the greatest, but it's worth it to keep everything organized.