Sentry looks cool. I have previously tested Rollbar and Airbrake, but was deeply unsatisfied with both.
The big problem I have with all these services is that you need set up each application individually: Each one is a silo, with its own notification settings, API key, and so on. We have dozens of apps (several products + lots of microservices), so this is just unacceptable. I looked into whether I could use a single API key with Rollbar or Airbrake, and simply tag each event with the name of the sender, but it turns out this is not feasible. They don't even have APIs that let you programmatically configure apps remotely.
How does Sentry compare?
(Many other SaaS services suffer from the same issue; for example, Semaphore, which we use for CI, requires a build script for each project. We worked around this by letting the build script be a single curl command that pipes a remote script to bash, shared across all projects. But hardly ideal.)