I just thought that I would give an update on the GR8's.
After 2 weeks of use (about 2-3 hours a day), the left driver developed some problems. The highs started to get harsh and the bass became very distorted. I didn't drive them too hard: straight from a MacBook Pro at a volume of 2-3 clicks.
Since it was fresh out of the box, I first thought that there was something wrong with the Mac. But when I plugged my Etymotics in, they were clear as can be. I tried the Grados with my iPhone and the distortion was still present.
I was fortunate enough to be able to return them and get my money back (the store didn't have another pair in stock). I am unsure if I will get another pair, since I just replaced them with the Senn. IE8's (I'm still testing the waters...).
The Senns. should arrive early next week. Hopefully my memory of the Grado's sound will hold up so I can do a comparison.
Oh, two things (one related, the other not):
The GR8's are compatible with the Comply T400 tips. (it's not mentioned on Comply's site yet)
Has anyone else noticed the tremendous bass performance of the new MacBook Pros when coupled with low-impedence IEMs? The MBP makes the Etymotic ER6i sound amazing and gives them a substantial boost in the low end (I would describe it as rich, and punchy, not forced or bloated).