Bug ? You want to enforce "Steps / Seen /Expected" structure". And maybe hint that people should estimate the severity / criticity / cost to fix.
Feature ? You want to optimize for people discussing the spec, and make it damn easy to know which decisions have been made. Bonus point for baking the "five why" in.
Task ? For developpers, Optimize for splitting the task in smaller chunks, and make it very easy to give dependencies between tasks.
For managers ? Optimize for letting the developpers rank the risk of each task to make it possible to estimate the overall risk of a set of features.
Product Owner ? Aggregate features / tasks into roadmap that compute the percentage of each billable feature that is actually done. Associate a risk to selling something that is in the roadmap, but done done yet. Make it harder fo sales to still sell a feature that had knowingly 2% chance of being done by demo day.
Sales ? Optimize for knowing the assumptions under which they can sell the stuff. Maintain a FAQ and list of caveats for your product ("does it work in China ? How much x do we support ? Etc...)
See a pattern here : every user of a task system expect different things, and it's hard to make a system that transition from a role to another.
Much easier to make another to do list on steroid with a poor text editor, a poor forum, and poor gant chart, etc...