We have done this quite a bit. The real time waster is trying to modify your beam/column/gridline locations in Risa. I usually get the model pretty close to perfect, then export to RISA, and see where the problems are (columns not on gridlines, beams not attached, etc). Then I go back to Revit, fix the problems and do a fresh export to Risa. I feel more comfortable modeling my loads, diaphragms, and other structural stuff in RISA. I have successfully done the bidirectional link, but usually at some point in the project I give it up. Because you want to keep your Revit model detailed/perfect and your Risa model can be approximate and simple.
We have also had good success with linking Revit and Risa Floor.
I've been referring to building projects. I had great problems exporting my Concrete wastewater treatment facility REVIT file to Risa 3d for plate FEA. At the time they were trying to improve that functionality.