I’ve used it in the last.
Monitoring in terms of APM its great if they instrumented well for your stack. I used c#/.net and has insights on day one that we’re actionable.
Logging - never tried this. Giving their pricing I imagine it’s expensive
Alerting - using synthetic checks is great. I thought it was pricey and just recommend pingdom if you can get away with it.
They also have new relic infra and that product with its built int alerting has definitely saved me. I’ve used the process monitoring to identify stability problems.