I have previously written about my experience signing up with pingdom services. I have opened a support ticket and and now my account has been moved to the proper tier. Nothing to complain about since then.
Actually, I was moving some setting up some services on a pingdom-monitored host and messed up apache's ssl configuration. Pingdom kindly alerted me via text (sms) about that. Nice.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko