What is the difference? Wordplay?

The two sentences have slightly different meanings. If I say, 'The work has been done', I could refer to any past time. If, though, I say 'The work is done', the implication is that the work (as something expected or required) has now been carried out and completed. The boss rushes out to me and demands, 'Where's that report. Is it ready yet'. I reply : 'The work is done. I've just finished'. I wouldn't say 'The work has been done'. That might prompt the reply : 'Then why didn't you give it to me ?' So I can see the two sentences as appropriate in different contexts. 'The work is done' isn't ungrammatical : it's elliptical for 'The work is [in the state of having been] done'.