My first audiophile headphones were Grado. About 5 years ago, I bought some SR-80s. I used to listen to them out in the city (despite them being open, and therefore levels of background noise rendering that rather pointless) plugged into a Zune, and at home plugged into a Cambridge Audio Azur 5XX something or other.
I caught the bug, so upgraded to the SR-125i's, then sold those again and bought some SR-225i's. Finally I bought some SR-325i's (had those at the same time as the SR-225i's).
I enjoyed listening to them, but comfort was a huge issue, in particular with the heavy 325i's. They just hurt you after any extended period of listening. And as mentioned by others, they could be very, very bright (325i's in particular) which again, I found fatiguing after a while.
I sold them, and picked up some Denon D2000s, which I had for a year or so. These sounded less exciting to my ears but so much more comfortable. Got rid of those too, though.
Now I own Fischer Audio, exlcusively. Got FA-002W, FA-006, FA-004. I must admit I do miss those Grados from time to time, but overall I think what I have now is superior.
I do have vivid memories of being blown away by the sound of Sam Cooke's voice in Night Beat, and Joni Mitchell's in Blue on those Grados. At the time I thought the way the Grados handled their vocals just incredible. Now, I'm not sure if that was the case or not... perhaps I simply had lower expectations prior to hearing them.