Pros: Mighty attack, juicy mids, unsibbilant highs. No need for amping.
Cons: Could get uncomfortable, listening to loud recordings is punished by harshness.
As someone already had stated- the Grado SR80i gets left in the shadow of its less costly sibling- the SR60i. For me the choice was quite easy- I had a hundred bucks to burn for my first serious headphone, so SR80i was the best thing that I got in my sights. I had heard that the SR60i is a great performer and the SR80i should be all that plus more- the choice was easy.
First thing that I liked about them even before listening was the cable- it was nice and thick about the same diameter as a normal AC cable. When I looked at the grills it was apparent that if needed the resoldering should be a breeze. The 1/4 to 1/8 adapter is the most solid I've ever seen- when plugged on it seems like a natural extension to the plug. Other than the wire build quality seems sufficiently well, construction is light so these headphones won't break if dropped. Just try not to step on them. When reading about the Prestige Series Grados one thing did upset me- many people complained about the comfort. For my average sized head the clamping isn't too much though sometimes after longer (4+ hour) listening sessions my pinnae seem to press through the stock foam pads. But after a little rest it's all good again. I don't have very thick hair but the metal band pressing on top of my head was never a problem.
Now about the sound. First of all these headphones do benefit from burn in for about 50-100 hours. When listening for the first time my jaw positively fell in my lap but now I'm confident to say that at first they sounded a bit thin and harsh. After the burn-in they get a bit more gentle and the bass blooms too a little. Bass wise they are a little too tame though you can hear the stated 20Hz low end and it will be more than enough to get that great PRAT for rock and jazz. One thing you must keep in mind when feeding these phones- as higher end headphones sound terrible when not properly amped, these sound terrible when fed with the wrong records. The SR80i absolutely hates the loudness war. If you dare to listen something compressed you WILL feel like in a war! Your teeth will clench and you will tire and think about running to the hills. When I first listened to some of recent pop-rock I felt like fighting. Since then I've listened to just about everything Steve Hoffman has laid his hands and ears on. For some time I thought that from now on I won't be searching music by artists but by audio engineers. But there are many others who aren't sacrificing dynamic range for fast sales. And those are the ones a Grado listener must have. You must keep in mind that Grado is (in)famous for tuning his products to his ear, so in some sense your taste must match to his. The SR80i does not have the wide genre bandwidth of some closed phones or IEM's but when at it's best it sure does not sound like 99$.
The SR80i is a higher fidelity headphone in sense that it does not try to cater everyone. It IS a highly polarising headphone and that is visible to anyone who has read more than a few reviews. If you like to listen to 60's rock, blues, jazz, funk these might be all that you need. The sensation is closest to using a guitar amp for a pillow.