I've just taken a look at your code and I think it's quite neat.
I've implemented it the other way around (i.e. a log-methods that receive a dumb Level enum) but I kind of like your idea of putting the log-methods into the enum instead.
This leaves the Logger interface alone, which is nice.
It should be extended by the various other methods, including isEnabled(Logger)/isEnabled(Logger, Marker), though - as you said.

Thanks for letting me know,
Joern.

Thanks - actually I'd prefer your way, it seems more natural, but I could do this way without needing a change.

I've just tidied it up using reflection to make it much easier to add the missing methods, though probably at a small performance cost.

Rob