These are primarily messaging systems. I've considered using them before. Nothing, however, has come close to letting me do introspection like Resque does, and the best part is that I don't need to do any work to get it.
For me it was because I was unable to access the log files if a job failed since I was on Heroku. Also it gives me a general idea of how the system behaves; in one second I can tell if the system is normal. I can tell if I need to bump some workers up for a certain queue. Basically it saves me from creating my own 'dashboard'.
