If I may, there are criticisms from academia in particular and concerns raised about the importance of a robust public domain. The difficulty with that argument is that there's very little evidence in practice that the economic or other implications of term extension are in fact a net negative for creativity in the public domain.
Then there's also the very practical consideration that, in reality, all that happens is that third party commercial entities end up taking advantage of works that fall into the public domain. The most recent example that I can think of in Canada was a record label that began to put out re-releases of public domain sound recordings for its own commercial gain, with no benefit for the artists who recorded them or for the entities that originally financed those recordings. It's very difficult to see who wins from the refusal of the government over the last many years to follow suit and join its international trading partners with a longer term for copyright.