Not much beyond looking at the product pages. The only piece of Office 365 that we are in love with is Word. Slack is the choice right now for us because we can use G Suite as our identity provider for SSO and the Slack integrations that are available for other products we use as well as our internal system.

The effort barrier just to get Office 365 to use G Suite for SSO keeps us from seriously deploying any of the other Office 365 features. It seems MS has made setting that up particularly annoying while almost all other app/providers have made it blissfully simple. We would probably be more likely to move to the new Hangouts Chat as a slack replacement, just because we are much more likely to continue to use Gmail/Calendar vs ever moving to Outlook 365/Exchange.