So I finally got my t50's in yesterday. Pretty good stock cans overall for the price, but I couldn't wait and tried the phat-pad modded-ad700 pads on them.
Please note my pads are at least third-hand and the outer material around the mesh that attaches it to the cups is deteriorated quite a bit.
Compared to stock, they are more comfortable by both keeping my ears colder and bringing the drivers further away from my ears so they no longer rub against them. Sound-wise, soundstage has increased dramatically, as well as a more airy presentation. While I didn't have a problem with the stock pads seal, these seem like they would be more forgiving for various head sizes and seal better for some having trouble with the stock pads. Bass impact is dramatically reduced, however, highs are much more textured. I do feel like there could be some sibilance there, but my ears aren't trained enough to tell. It no doubt these pads are a huge reason for the AD700 soundstage. If I could somehow keep this airy feel while bringing the old bass back I would be extremely happy with these.
One thing to note however, is that while the seal between the pads and ear are generally better, the seal between the pad and headphones fits like a glove, but appear to leak sound. It could be because of my chewed up pads, but it seems to me like some sound is leaking between the pads and cups somehow.