A long awaited pet project of mine (suggested by Evan and others) has finally landed in the 1.8 branch. Upon entity loading, Elgg now prefetches all entity metadata values using very few queries. Generally one query per elgg_get_entities() call. I've not done direct query count comparisons, but I see frequent cache hits in the code path in xdebug and foresee this making a huge difference on pages with a lot of enties.

Great care has been taken to handle lots of cache invalidation cases, and pretty thorough unit tests are included, but this is a big commit with a lot of moving parts.

If you have access to some test sites following the 1.8 branch I urge you to check this out and report any funny business. And of course let us know if it's faster!