Used my set of Fit-4-All Music at garage day today... And I have to say I'm impressed. I had no ringing or discomfort during or after the jam. They were as comfortable as can be expected and did an amazing job of preserving guitar frequencies so I could still hear myself. It's also perfectly possible to hold a conversation with them in so I didn't even take them out between songs.
My only complaint is that they made singing significantly harder. I really battled to pick my voice out of the mix, even with the vocals turned right up, so I pushed a lot harder than I needed to and my pitching was probably a bit wonky. Don't know if there is any way around this short of in ear monitors.
Still, great product, I would definitely recommend.