MongoDB 0.9.9 Released
blog.mongodb.org
blog.mongodb.org
I looked at using John Nunemaker's MongoMapper library to integrate MongoDB into my application (see http://github.com/jnunemaker/mongomapper/tree/master). It looks great!
My current concerns are with tiny little nits in the API. But these are minor and there seems to be a way to do everything I need.
The replication pairs are very interesting as it allows automated failover. WIthin your code you specify a list of the servers and it will automatically set one as the master. If that fails then the others will negotiate which one will become the master and take over without any need to change your code.
Sharding is experimental and isn't documented or recommended for use at the moment so I can't comment on that.
We're also using the commercial support option to guarantee us 24/7 response if something goes wrong and to get bug fixes quickly, which we have used once so far.