I really want to like Producteev. It's free, we can have as many members as we want, clean user interface ... but there is one thing missing: Task Description.
When I say "Task Description", I mean like an "initial" comment that would show up at the TOP of a task. Now yes, there are Subtasks, but they only allow for one line of text each. I'm talking a field that would allow for paragraphs of text if necessary, where I can attach files, like a Comment.
Example: For my game development team, just posting a Subtask for one of our Concept Artists that says something like "Draw ____ armor" does not cut it. They need a description for what the task is asking them. Yes, details could be posted in a comment, but the big issue is that that initial comment will be dropped to the bottom of the comment page!
if you don't know what I mean, check out Asana. Every task has a "top comment" to it. Heck, if it weren't for the 15 user limit we'd probably go with that tool just because of the inclusion of that one feature!