I recently put a sheet of Rasant Powersponge onto my blade to replace a very old and tired sheet of Tenergy 05-FX. After seeing this thread, I thought I'd add my thoughts comparing the two rubbers.
The first time I played with Rasant Powersponge (RPS)
Positives
1.) It felt lighter than 05-FX, so it balanced my blade nicely (I play with 0X pips on the backhand).
2.) It felt a lot less sensitive to spin than 05-FX. A number of balls where I blocked a topspin shot from my opponent went back onto to table where I directed it to. With 05-FX these balls are harder to keep down.
3.) There appeared to be more of a catapult when I hit the ball hard. I could feel the ball sink into the sponge and it really fly off the rubber. When brushing the ball, it was noticeably slower. I can only deduce that this means the rubber has more gears than 05-FX.
Negatives
1.) During regular driving (like warming up forehand to forehand) it felt mushy. I can only put this down to the softness. 05-FX feels very direct and positive. Where you aim the ball to go, it goes.
2.) It's not a spiny as 05-FX and my serves did not have the same bite. In fact, my 05-FX is fairly old and has been used all season, so it's not a new sheet. I still felt that I could generate more spin with it compared to the RPS.
3.) It might just be that I'm still not familiar with the rubber, but it either felt very slow or quite quick. I'm sure it's just playing time but I found it hard to judge the middle ground of balancing speed and spin.
The second time I played with Rasant Powersponge (RPS)
1.) The original "springy" nature that I felt when I first tried the rubber appeared to have disappeared and I found that I was able to place the ball onto the table more easily than before. I asked myself if I thought it had better control than 05-FX and to be honest I can't say that it does - It just feels different. It has a much softer more mushy feel to it whereas 05-FX has a harder more positive direct feel to it. That's the best way I can summarise it.
2.) As before, I found that the RPS appeared to be less sensitive to spin, so blocking back top spin felt a lot easier compared to 05-FX.
3.) I've convinced now that the RPS has more gears than 05-FX. It's easier to play slow brushed loops and when you hit the ball hard, it cannons off - You really feel the ball sinking into the soft rubber when hitting hard. However I can't say that it has the same top end speed as 05-FX. It's difficult to tell as when you hit hard with 05-FX, you feel the vibration through the blade whereas when you hit hard with RPS, a lot of this vibration gets absorbed into the soft sponge which masks the feeling of power and speed.
4.) The RPS is quite a spinny rubber and I could get very good top spin on my brush loops. However I didn't feel as if I was getting the same savage bite that 05-FX offers me, especially when serving.
5.) I "feel" more of the ball contact through the blade with 05-FX whereas the softer feel of the RPS makes that ball contact feel more dulled. This is neither a bad or good thing, it's just personal preference of what you're used to. I found this softer mushier feel a bit off-putting at first but after playing with it for a while, it felt OK.
6.) If you smash the ball right (and I only managed to do this a couple of times), the ball really flies low and arrow straight. You hear the crack of the ball as it hits your blade and a split second later you see it skidding off with a low bounce at the other end of the table. I can't do this with 05-FX as the ball tends to bounce more...maybe it's the throw angle, I'm not sure, but it's a very effective shot if you can time it right.
7.) Although I have more control (I think) with the RPS, it doesn't communicate this control was well as 05-FX. With the Tenergy, I feel that I can judge the pace, speed and placement of the ball much more easily whereas with the RPS it feels less accurate. I don't think it actually is however, it's just that the softer mushier feel is going to take some time to get used to.
Overall I really think RPS has potential and I'd like to spend some more time with it. I still intend on buying a sheet of Tenergy 80-FX when it becomes available, but in the meantime, RPS will stay on my blade.