Problems with sustainability as it is currently understood:

• The idea of limits to growth and resources exhaustion don't have much credibility in economic circles because catastrophe has been predicted over and over again and has failed to appear. Advocates of limits to growth would do well to study this long history of failed predictions before blithely claiming that “this time it's different.”
• The whole concept of what sustainable use of nonrenewable resources would mean bears some thought. How long are we planning to sustain life on earth?
• it's hard to see how the sort of change some envision could come about without either unlikely changes in human nature or enviro-totalitarianism.
• There seems to be some tendency to suppose that some government hierarchy of eco-mandarins must take over from the markets, directing what must be produced and how, for the good of the masses (who would otherwise choose something else.) This fails to consider something that economists know well, which is that central planning is inevitably less efficient and less innovative because it can only draw on a small faction of the knowledge and skills present in the society as a whole.
• Economics has some things to say about conservation, especially the Jevons paradox, that increases in efficiency that pay off quickly rarely reduce energy consumption by as much as you would suppose, and may even increase consumption.