The HD25-1 is pretty impactful as it has good speed. It is not the bassiest phone out there, and the treble can be sibilant and spiked which while not making it sound thin, can take away the 'fatness' of the music sometimes. Nevertheless, rock/metal is tackled perfectly well by the HD25.
As others have said, it can get hot in summer and the stock cable is a noticeable dragger-downer of sound quality, but it also happens to be a superb cable for portable use as it doesn't bind to anything as rubber-coated cables do, it's short, it has a right-angled plug which fits virtually any portable properly and reduces stress placed on the headphone jack.
I've just acquired the AKG K181DJ... and it's my feeling at this point that it is just another phone which doesn't quite measure up to the 25 as a portable phone. As I've said a few times before, the HD25 is not the best sounding phone for $200, far from it. However it is the combination of durability, portability, usability, light weight, isolation and reasonable sound that makes it the top portable headphone for me to date.
One of the also-ran alternatives worthy of mention is the Audio-Technica ATH-ES7. While the HD25 doesn't look too dorky on most heads, it is nevertheless rather 'industrial'. The ES7 is definitely more socially acceptable. I don't find it as comfortable (this is relatively speaking... the HD25-1 start to slightly hurt my ears after a couple of hours and if I wear them continuously, by the 4th hour they have got to come off for the rest of the day) but the sound is milder than the HD25 but is still capable of attacking reasonably when called for, inferior in clarity but still offers decent resolution, and delivers prodigious amounts of bass. Attractive-looking, good fun cans if you don't mind the significantly lessened isolation (I do).