I am not a developer, but do know about translations, speaking 3 languages fluently and getting by with a few others. I worked with Joomfish about a year ago - more as a test and learning experience. Was happy with that experience, but decided to try Josetta out also a while ago. Both I believe are good tools for administrative purposes, which what they should be. Translations are for humans and cannot be replaced by computers. Anybody who thinks so and uses Bing or Google, just puts loads of garbage on his site. The documentation of Josetta is very good and getting "Bing" lined up was no issue for me (never managed with Google for Joomfish)-but considering the above statement- of course, I used it only once or twice.
After switching back from Drupal to Joomla for some sites, I am happy to use Josetta and have friends work with Joomla work-flow on the front-end without messing up my sites.