We've been doing this the last four brew sessions with the 5 gallon paint filter bags from Lowes. They work awesome and are cheap enough to be disposable. We get an extra half gallon of good wort at the bottom of the keggle into our fermenter. We even went so far as to modify the dip tube to get more of the wort.
The only downside we have found is we have to monitor the bag during the recirc to avoid it becoming clogged and overfilled. We leave our spoon down in the bag and occasionally scrap the inside of the bag to push the material to the bottom of the bag. A small amount actually escapes but it is minimal. When we flameout and start cooling, we continue to recirc to the boil keggle for a couple of minutes and capture the initial cold break being formed in the bag as well. The break material forms quickly in the heat exchanger and keggle as the cold wort flows back in, but quickly clears as it is recirculated. Once it clears we begin filling the fermenter.
The upside is clear wort, and more of it, into the fermenter. And that's a good thing...
