Well, since it was asked...! Yes, visibility is very curtailed. This past summer I would (on a whim or a dare) ride around my small town on my motorcycle while wearing my MRCE. It was fun; to begin with. I live in a touristy town and there were a lot of thumbs up, honks, waves and pictures taken. Then, I found a patch of sand on a corner that I'm sure I would have seen had I not been wearing the bucket. On top of that (hotdogging) I took the corner faster than I needed to do. I ended up wiping out and fracturing my right humerus, scapula and ankle.
As much fun as I had, I can tell you I will NEVER again wear a bucket which blocks my vision so much while on a bike. I'm a 25 year motorcycle rider and thought I would be ok...I was wrong. Don't try it guys...(and gals), it's NOT worth it.