I remember when support for them just appeared and you had to LD_PRELOAD a shim IIRC to make Postgres actually use them we jumped on it, enabled them immediately and got a pretty significant boost, around 15-20%, yes.

That was idk, 2008-9 -ish? I don't know what spotty history you are talking about, if you have multigigabyte address spaces floating on a machine it's stupid not to use hugepages.