Comparing Log Levels Across Languages

Personally, I like having Trace & Debug, though I could do with just one in a pinch. In particular Trace feels useful for some types of library code. Info seems the right level for startup notices and anything that happens regularly.

In practice I don't find myself using Warn very often. Error seems straightforward, but I have a tough time wrapping my head around Critical, Alert, Panic, Severe and such. I would love to hear about someone who feels like they're effectively using those levels.