At Netapp I worked for a bit on a content addressable version of a filer where each 4K block was hashed and the hash became the block address. Unlike Ugarit the block hashes were in an SSD based metadata server rather than being hashed into directories. The feature that fell out of this was you got content deduplication for 'free' since any block that hashed to a particular code you already had stored you didn't need to store again. (and this exploited the fixed length defense against hash collisions).
Largely, Ugarit is ticking along nicely in my production setup, doing backups of my servers; when I get time I work on (a) performance, which is still weak in some cases and (b) archive mode, which is a fun spare-time project rather than something urgent I use. But the core case of doing backups Just Works(tm).
Mature: Well, it's been running nightly for years for me, and has saved the day on a few occasions when I've had to restore stuff from the vault.
Reliable: The only data I've lost was when a vault disk actually died, and I hadn't replicated it because, well, I was happier losing some history sometimes rather than buying more disk for that use case. However, when I get archive mode in production, I'm going to build a better vault replication solution than rsync!