I will say that from my experience in the 1980s, a lot of those spaces were transformed into kind of funky residential space. The factories are always located on rivers, many of them scenic. In Deep River CT, in the the 1980s there was an old factory located on a tributary river for the Connecticut River. It was called the Piano Factory. That is literally what it was. I knew an old lawyer whose mother worked in the factory. He remembered vast river barges being towed up the river filled with enormous elephant ivory tusks. The keys were made from the tusks. There is actually a section of the very wealthy town of Essex that is still called Ivoryton.
    In the 80's the factory was converted into a very successull Condo development. The prices were maybe 80,000 bucks. A lot of the places had fabulous views. The prices increased and the values held. These factories are always situated on a river. who knows?

The University of Waterloo School of Architecture campus in Cambridge, Ontario is similarly housed in a retrofitted silk mill: http://www.architecture.uwaterloo.ca/ourbuilding.html