Wouldn't the Slack bot integration provide a better moat. If they can get orgs using a lot of bots for CI reporting, etc switching gets more difficult at least. Not sure how many teams get that tightly integrated with bots though.
If we need to switch to a different messaging platform, sending that same notification at a different api should be pretty trivial. And if it isn't, I don't know why we'd be switching.
- deal with the target platform's API
- deal with APIs of the many platforms that are being integrated
- maintenance and SLAs
I honestly doubt you can create half a dozen good integrations that require more than just notifications in a channel (for example, PagerDuty notifications and the like).