OK, I'll provide a user's perspective as we are invested in Mongo as a storage system for statistical data and have been using it for a good few years now. MongoDb has been, so far, very good to us. I did not experience any of the problems people sometimes cry so very vocally about. My main concern about Mongo is actually one that is addressed by this release so I'm quite excited to try it out - data compression. Mongo is generally quite irresponsible about disk space usage. Yes disks are cheap but I rather not have a 2TB dataset if I can have half the size, thank you very much.

As a side note, the hype from MongoDb the company equals the anti-hype you get on places like HN, so I guess they even out.