I agree that this sense of 'mean' should definitely be added. (But penguin, no real dictionaries? Tsk tsk, with all those links at the beginning of New Entry and all the red print and everything ... (-; )
It's not just excellent; the diction is less formal, and the meaning is really more like 'impressive,' with a tone of both admiration and mild competition.
It might be good to give an example sentence, too. You can't use the adjective alone, only before a noun (not *'His potato salad is mean' but 'He makes a mean potato salad'). And it's usually after an active verb in the present tense, showing that the person does the thing consistently well, as a habit.
Like Hein I can't support 'besonders niedrig'; not sure I even understand the reasoning behind that one. The 'mean prices' in the example from the previous thread was IMO just a poor choice of words, as 'mean' there could mean either 'fies' or 'spitze,' though obviously the latter makes more sense.
The sense of 'mean' as 'low' in the sense of social status is largely obsolete, and other similar senses like 'inferior' are no longer common. The only exception is the fixed phrase 'no mean ____,' and LEO already has 'no mean feat' as an example of the sense 'not half bad' or 'not shabby.'
I think I would vote for 'spitze' and maybe 'stark' on a similar diction level, and to explain the meaning the best, 'beeindruckend.'