Recs.
Updated
Axosoft is now GitKraken, available as a hosted or self-hosted version (for Windows). The GitKraken client can be used for free (by one user).
SpecsUpdate
Pros
Pro Extremely fine-grained control over the lifecycle of each task
Tasks are divided into categories and each category can have one or more workflows which are followed by tasks belonging to that category until their completion.
In other words, workflows are used to set each step tasks need to take in order to be completed. Axosoft lets users have extremely fine-grained control over workflows and by extension, the whole lifecycle of each task. Each step in a workflow can be named and you can choose which fields are updated when a step is complete. This way you can automatically tweak tasks as they progress (you can set tasks to belong to different users once a step is complete, you can even change workflows for a task if a certain step is taken).
Cons
Con Can get rather expensive quickly
Axosoft can get pretty expensive pretty quickly for large teams and/or large projects. The cheapest tier allows for a maximum of five users and costs $20/month. However, for larger teams and larger projects it can easily go into the thousands of USD per month.