For the folks out there using Tornado in production, what database (if any) are you using it with? Are you using an async interface to your database (assuming one is available)?
I honestly was a bit frustrated with it from a development standpoint because of all the callbacks. Just felt like spaghetti code. Since I have started applying tornado.gen its been pretty effective.
Asyncmongo may not fit all use cases though. As I understand it it can be difficult to deal with paging potentially based off of what I have read in the issues on the github repo. Also last I checked it doesn't support tailable cursors.
One thing to note is that with friendfeed they did synchronous requests to MySQL and their thought was you should make sure the requests responses are quick enough that blocking is not an issue. After working hard to do asynchronous requests I'm now of the opinion I should have taken their word for it.
For both Mongo and Redis I use the sync libraries. So far, I don't have any slow queries that would require me to async them.