I've been playing Jeff's duds for several years now. They are my clear favorite tip ever. I find them to be med/hard but very forgiving. They grip well, but I would not say it is impossible to miscue with them. With poor technique miscues are quite easy to come by with these tips, as with any other.
Ease of maintenance, consistency and longevity are the strongest suites of these tips. The last one I took off after a year just to see if their was a difference in a new one, there wasn't, it felt exactly the same. This was twice weekly play all year long, maybe five or six hours a week of actual play. That's pretty damn good in my book. I have had a Kamui last that long but it was also a flat tire when I finally pulled it off, and it went through the normal cycles of hardness and adjustment. These tips will play pretty much the same throughout their lifespan. If your the type that shapes your tip once or twice and then leaves them alone, these tips may last you a couple of years! The only reason I have to change them is I now shape them regularly and eventually they are too short, at three dollars I'm not really concerned about saving money here. With forty dollar tips I feel compelled to get every last shot out of them, for better or worse.
I strongly recommend these tips to everyone!