You should read through PostgreSQL release notes some day.

"20% consumption" is more a factor of how much memory you have installed and how much you intend to use than PyPy's maturity. I frequently use malloc()/mmap() to consume much more than 20% of system memory.

EDIT: strike this, I misunderstood.

I think they're talking about a 20% improvement in memory consumption release-over-release, not complaining that it's consuming 20% of their memory.