We use it a lot at the webdev company where I work (and at home). But often it lacks some features. For some we decided to make a module to solve this (We, as the company I work for).
The first module I developed adresses a missing feature in multilingual sites.
It adds the ability to disable Language neutral for nodetypes and also to specify a default language for node types. These were features that not only we were missing, but we also found them to be missed by other drupal users.
The module adds some fields to the Workflow settings fieldset where you can disable Language neutral and choose dynamic (user language, interface language or no default language) or fixed (any language available in the system or language neutral) default language for the nodetype.
The code complies to the coding standards and is checked with the devel module. I have also included SimpleTest tests.
I hope you have enough information to evaluate the module.