Actually i have been using it for more than 3 years with zero issues using on the fly compression. Btrfs was officially declared stable when it was taken out of the experimental phase in the kernel by 2012, when several Linux distributions moved Btrfs from experimental to production or supported status.

The only features "still on development" would be raid 5/6 modes, raid 0/1 and jbod are perfectly fine.

With btrfs you can mix and match different devices and use them like a single device: https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices

There are several guides on btrfs out there, most distros have recent enough kernels to safely use it already.