First off, Comfort is both a pro and a con, let me explain. In the short term, these light weight headphones are very comfortable. In the long run however (1 or more hours of use) they get a little scratchy around the ears. I suggest taking them off every now and then to refresh your senses!
As for sound, it's extraordinary for headphones of this price. I would argue there isn't anything better for less than $200, or even $250.
I use these with a NuForce headphone amp, and I've extremely impressed with the sound. It's very clean, very dynamic (depending on the recording) and has alot of impact. With most rock music, these are very immediate with drum hits, and the mid range is very detailed.
If I were to say a few more things, I would say they have a ton of texture in the sound. They make music enjoyable again.
As a final word, I haven't been this excited about a pair of headphones since I purchased a pair of Etymotic HF5 earbuds for $120. Those by the way are also outstanding for the price. Just like my Etymotics, I would say these Grados have the same value in the fact that they sound FAR better than anything else for the price.
Pros: Best in class, very dynamic, very immediate, Comfort
Cons: Appearance, Comfort (Pro and Con there)