What features would you want in a logger?

Here's what I'm planning so far:
- Tagged entries for easy scanning of log file
- Support for indenting to group similar sequential entries
- Multiple entry types (normal, info, event, warning, error, fatal, debug, verbose)
- Meta entries, so the logger logging about itself, e.g. disk i/o failures.
- Ability to add custom entry types, including tag, log-level, etc.
- Customizable timestamp function
- Support for JS's async nature -- this equates to passing a unique key per 'thread'; the logger will re-write all the parent blocks for context, if necessary. if that sounds confusing, it's okay; just trust that it makes sense.
- Caching, retries, etc. in the event of disk i/o issues.
- Support for custom writers, allowing you to e.g. write logs to an API rather than console or disk.

How about these features?
- Multiple (named) logs with separate writers (console, disk, etc.)
- Ability to individually enable/disable writing of specific entry types. (want verbose but not info? sure thing, weirdo!)
- Multiple writers per log. Combined with the above, this would allow you to write specific entry types (e.g. error, warning, fatal) to stderr instead of stdout, or to different apis.
- Ability to write the same log entry to multiple logs simultaneously

What do you think of these features?
What other features would you want?
I'm open to suggestions!