Though you're not entirely wrong on the stability issues, I've been beta testing the next update (releasing soon) and there are a LOT of fixes there. The Cycles rendering system is unique in that it gives your more flexibility than Octane does, and that's not including the very deep x-particles integration. There are also a TON of resources in the already established blender community regarding how to work with Cycles. A majority of the issues in the initial release have been due to incompatibilities in the Cycles core, not the Cycles Cinema 4D bridge. It's also fast, renderes beautifully, and works on CPU / CUDA fantastically with solid OpenCL support coming in the next Cycles Core now that the split-kernel is complete (and then integrated into Cycles 4D),
Small forum activity isn't really an issue. I've found that there are a few posts a day, but again, this is a brand new renderer in a sea of rendering engines. Also the developers frequent the threads and will usually get back to you within the same day. Also the users that do participate are generally very knowledgable.
Octane is a fantastic renderer, and pretty much the industry standard for now, but Cycles is deep and I think their nodal system and the way you create shaders/materials is superior to the rest solely for the level of intricacy that you can control. For anyone in Motion Graphics/Design, I think Cycles is one to look out for as I feel it has a lot of growth potential.