The effects are going to be harder to notice if you don't have a naked PF. I know that I thought for years that I was pulling fantastic shots (and indeed they did taste fine) and then I got a naked PF and realized how much better my shots could be.
A video example of "the donut effect during beading:"
There are a few other examples on youtube, but I think this gets the point across pretty well.
Jennifer Graham said:
Wow, Brian, that just blew a few of the cobwebs out of my mind! Thanks for sharing the video. Now I want a flat tamper, a convex tamper, AND a naked portafilter, AND a tapered filter basket, and lots and lots of time to experiment. That was one of the most beautiful things I've ever seen, even though that wasn't the point you were making and the shot was overextracted. I've just never seen anything like it before. Thanks!
Uh oh. So it begins... :)