I've taken to mashing in a BIAB in my keggle with RIMS. It always seems to provide a clearer wort and easier clean up. This past week it saved me from disaster when the false bottom caved in. I had 33lbs of grain and 1.5 qt/lb water which was just a tad too much water for the volume of grain. When I transferred the first runnings to the BK it stopped a few gallons short and I realized that something had stuck. I simply pulled up on the grain bag and heard a sucking/vacuum release sound, after a few more tugs on the bag things started flowing again. Without the bag I would have had to transfer 30lbs of grain to another vessel so I could fix the false bottom.
I will never brew without the BIAB again.