I'm writing a pretty complicated application using parse. It's been great so far. I've been a very vocal non-fan of their iOS SDK though, so much so that I'm actually dropping it in favor of a custom written job using their REST API instead. But besides that one thing, it's been fantastic.
The new Cloud code stuff they just added is awesome.
I spent 10 years doing heavy backend shit until about 5 years ago when I switched back to native front-end development. I still am having to write a service here or there to cover some holes that Parse doesn't cover for this application, but those are pretty small holes.
A+++ would use again.