I keep seeing Sentry for exception tracking pop up all over the place these days. I'm using Airbrake now and the experience has been so-so (my main complaint is the slow interface). Is it worth the switch?

Sentry is great, and it's open-source. So you could run your own instance of it.

How is this a stack? It's a collection of third party providers.

Pingdom should probably not be in "Group Chat" category.

Nor New Relic in the "Email Marketing" category...