Thought I'd share my experience with changing the SHR440 pads to HM5.
When I received my 440 this morning they weren't very comfortable, the pads were stiff making my ears hot, they would apply pressure around my outer ear making it uncomfortable. I had some HM5 pads here which a generous friend gave to me. They went on no problems there was no work around needed, they're nice and soft like pillows. The 440 is now extremely comfortable also much more like wearing over the ear headphones instead of on the ear. My ears just sink inside the pads comfort has increased dramatically.
As for sound it's hard for to say because I changed the pads over so quickly and this is my first time with 440 so listening stock wasn't for very long. I can hear a gain in soundstage width, there's more depth to the stage left and right and tonality seems to of stayed about the same. Overall having these pads here today (new I might add) has been a real life saver. Highly recommend removing the Shure pads, they're aren't the nicest pads I've seen. Turn your Shure 440 into a comfort lounge. I must admit they look great now, love the look.
For those wondering where to buy the pads they can be found at MP4Nation.