Of the three rig failures I know of, two were mild, one was not.
I got to watch our commodore's 5.5 rig come down after a shroud failed - he was going downwind with his screacher out. The whole rig gently sailed itself into the water, sails drawing nicely the whole way down. I think we were all mesmerized by how gently and peacefully it went down.
I broke a shroud pin on my Hobie-18, and the rig came down gently enough to be able to keep clear of it, and that was in medium+ conditions. The biggest issue was the work entailed in clearing the rig and stowing the mast and sails so as to not do any damage and start the paddle home. Effort made a little tougher by the spinnaker rig. Times like that are when appreciate a good knife and some basic tools.
The not so gentle one I know of I didn't see - one of our Fleet members was crewing on an older Tornado doing some blast reaching in strong winds. He was on the wire, and when the windward shroud let go the rig went fast, and the trapeze wire flung him (trebuchet-like). Good set of bumps and bruises, fortunately nothing more than that.