My experiences with the development team are also very positive. I do some work around automation and conversion, and interface with LibreOffice for this. The recent releases are quite stable, import and export filters matured and as a whole it responds a lot faster.
Obviously, there are various things that can be improved more and various bugs have not been squashed yet, but the achievement of the LibreOffice project (and the Document Foundation in general) is that progress is happening, it happens at a fast pace, and anyone can help make it go faster.
Since I am not a C++ developer myself, I am bound to discussions with developers and reporting bugs. And even that is quite rewarding since new releases happen on a monthly basis, there is a fast turn-around time to reporting a bug and it potentially hitting the next release.