Firefox (with Firebug), Chrome, and Safari all have robust logging and profiling capabilities through the use of the console object. High-level information can be found about it here: http://getfirebug.com/logging
I would like to be able to do the same.
For logging (trace): I could write a Console object that was globally accessible and prepend "<<error>>" or "<<info>>" to the beginning of statements traced out with it, but could we have the console take messages that started with <<error>> and put a red icon with an exclamation mark next to it, etc.
For console.trace (could be called stack to avoid confusion): is it possible to get the current stack via actionscript and dump it to the console?
For profiling: this is the biggest feature in this request (most important). If we could programmatically start profiling and stop it we would have much better fine-grained control over data we need to see. We often know where a problem might be, but we can't profile just the one problem because we can only profile the app at a general level. It would help us so much to profile individual functions with a simple console.profile(); myMethod(); console.endProfile();
Other things like logging an interactive listing of an object to the console or grouping would be the bomb!