Thanks for the helpful info, I do still have one reservation about mongo however.

There is one thing that couch does to better than mongo, and thats single server durability. You can pretty much kill -9 couch and it won't care (that's pretty much how it stops itself).

Now, I understand mongodb's stance on why you should be running multiple servers for your high performance app, but for a lot of apps that don't need HA that's just overkill and a pain to configure (and extra $$$ for more hardware). In fact, I'd go so far as to say thats the case for most apps. If I recall they're working on it at the moment though.