i have the hd25's... they are comfortable. don't like the sony's due to the space ship factor and i don't have that big of a cranium... so it looks like i am wearing a helmet. if i put them around my neck, i feel like i have been in a car accident and am wearing a neck brace.
i'll stick with the hd25's for now....
as for slipmats.... i prefer the round kind.