Airbrake is easy to use, the pricing is great, and the granularity of the information is good as well.
It makes error-tracking simple, and I'm extremely grateful for it being integrated into Heroku for ease of use with my Rails project. Would definitely use it again and recommend it to others.
We receive notifications in our mail and slack, great for quick turn-around. Statistics are a nice addition.
It was really difficult to backtrace all log files to catch my apps errors and that was a waste of time, but now I can concentrate to fix them.
It has been my experience in the past in many different IT organizations to not find out about an error until the customer reports it.
One problem I faced is, UI is not very interactive for beginners. Some times finding some features becomes harder.