We're huge fans! Our real time search technology copied its architecture from Zoie, and our faceting/caching took some ideas from Bobo!

We didn't use them outright since we have fairly different requirements/constraints (our data has some pleasant properties that makes it easier to shard and facet than the general case) and we wanted something a bit simpler.

Shoot me an email sometime though (email in profile)! I'd love to buy you lunch and pick your brain ;-) You guys clearly know what you're doing!