I debated purchasing these because I wondered whether they'd worth the price. They absolutely are.
If you intend to spend long stretches of time working with your HD25s, or even just listening to music for pleasure, these make your experience much more comfortable.
HD25s can be, for some, a little tight on the ears. Over long periods of time this can cause some discomfort. These pads are very soft and do alleviate some of this pressure.
Similarly, listening for long periods of time with the regular leatherette style ear pads can lead to sweaty ears. This doesn't happen with these ear pads due to their soft fabric coating.
I was worried there might be some sound leakage compared to the original pads, thinking that the fabric cover might not allow for a tight seal. This isn't the case. I don't think sound quality is comprised whatsoever.
I think these pads a definitely a worthwhile purchase for HD25 owners. They really take your comfort level up a notch!