I hope they pay greater attention to the low and high end of their compression ratio spectrum. On the low end, it'd be great if it could exceed lz4 in terms of speed and memory savings. On the high end it'd be great to exceed XZ/LZMA.

Right now it's impressive "in the middle", but I find myself in a lot of situations where I care about the extremes. I.e. for something that will be transferred a lot, or cold-stored, I want maximum compression, CPU/RAM usage be damned, within reason. So I tend to use LZMA there if files aren't too large. For realtime/network RPC scenarios I want minimum RAM/CPU usage and Pareto-optimality on multi-GbE networks. This is where I use LZ4 (and used to use Snappy/Zippy).

At their scale, though, FB is surely saving many millions of dollars thanks to deploying this, both in human/machine time savings and storage savings.