The company I work at uses it across all products - Javascript and PHP. It's super handy and has helped us find bugs before our users! Definitely recommend giving it a shot since you can have Sentry logging your Javascript errors in 2 lines of code.
It is /very/ useful. I managed to mooch a free account for an open-source project and it has been invaluable. For Python projects, it has the best integration (being written in python) of any of the many that I have tried (most of which seem to focus on RoR and everything else is an extra).
I'm attempting to get it adopted at my workplace as well. The major point that seems to get the bosses interested is being able to host it ourselves (for free, it's open source) easily in the case that we outgrow the hosted version.