My first instinct was to not convert my games at home. However, these new rubbers are finding their way onto a number of TOPL hosts' machines, so I've had some game time with them. As someone whose pinball game consists of a lot of control near the flippers, this new rubber has changed things considerably for me. My observations:
1) New flipper rubbers are more dead, as it applies to bounces. A bounce pass doesn't bounce nearly as much. And forget those subtle little bounces off the end of your flipper. What may have cleared the gap and just made it across to the other flipper - no more. Where red rubbers have some bounce, black rubbers have a little less, these new ones are even worse than that.
2) New flipper rubbers are much stickier. Considerably stickier. This means drop catches stick like glue. And as is the case when you really get a good hold of a ball like that, you have to wait that split second longer for the ball to 'unseat' itself a bit before you flip. So, drop catches work great. So much so, you can do them substantially closer to the end of the flipper. (Live catches - I've not tried yet). Also, SDTM shots are more savable due to the amount of grip you get from the tip of your flipper.
Because of this extra grip and lack of bounce, the behaviour is different when you try to jam the ball into the lower corner of the sling, or trap the ball coming down your inlane at speed. The ball/'rubber' combo just doesn't react the way it used to.
3) Contrary to item 1), these rubbers seem to have more power. This potential energy shows itself when you smack the ball. This means more power for long shots. I suspect the 'rubber' is not as responsive at slow speeds (like that of a small bounce) but opens up when you hit the ball and really compress the flipper rubber. It does not have the usual characteristics of rubber.
I heard these are really difficult to stretch when you install them onto flipper bats.
My take? If these last as long as claimed (and they will), you will see more of them everywhere. If you play competitively, you will have to get used to them whether you like it or not. Do I like them? Not really. Rubber is rubber, polyurethane is not. Maybe I just need time.