Feature request: a site-wide estimate modifier / scaling factor / efficiency rating.
Individual users can say they spend "70% of their time on FogBugz tasks". However, even if the person is supposed to spend 100% of their time on FB tasks, there will be interruptions, questions, etc. So, I would not schedule 80 hours of estimates into 80 working hours.
Ideally, at the very least, I'd like to be able to give a site-wide or per-project efficiency rating. For example "all developers are 80% efficient" => a 40 hour work week should achieve 32hrs of "working on" when 100% on FogBugz tasks. A per project rating may also be useful to compensate for "new project with steep learning curve" vs "old and predictable project".
(I've also pondered a per user rating, but believe that would probably confuse personal estimates, working on and estimate accuracy too much...)