Our PagerDuty is integrated right now with Scout, Pingdom, and our own custom alerting system.
So far most complaints we've had while using the service for the first week were our own faults: for example, our monitoring was too sensitive, which was fixed by using the regexp filters, and by eliminating spurious errors from reporting on our side. One thing that PagerDuty did was that it basically forced us to fix these reporting issues so that we weren't woken up at 5AM unless it was a real emergency.
The SMS interface got a little confusing when we had two errors at once. For example, a frequent case is getting two pages at once, "Service X is DOWN" and "quora.com is DOWN". I think what I tried doing was:
1. Receive the first report (site).
2. Receive the second report (service).
3. ACK both reports using the second report's code.
4. Fix the service.
5. Attempt to resolve the second report, receive a "code already used" error.
Resolving things via SMS is a little bit clumsy (it's what I usually default to). A link to the PagerDuty login would be cool, but I don't know if it would fit in the 160 character limit.
Don't get me wrong, it's absolutely brilliant. I think it's the first time I've ever given a thumbs up to a third level metasolution to a problem.
Pagerduty needs to push some use cases on their site. It might break the SaaS reluctance to steaks and strippers type corporate managers. "It can eat my rediclously complicated jasper report that I send straight to the trash bin on arrival so I don't have to read it and figure out what buttons on the phone I have to push with all the reluctance of a four year old kid with a plate of brussel sprouts and broccoli in front of them? Sign me up!"
The fact that it doesn't do monitoring is pretty much my only major gripe with PagerDuty. I've been a customer for a few months.