I got a pair of these in yesterday. After listening last night and for the past few hours, the first thing I have to say is: whoa!
While it's still too early to call this my new favorite headphone (my K701 is currently out of commission and my AD2000 is gone), I can say that the RS1 is the most amazing Grado I've heard to date (have heard SR60, SR80, SR225, and SR325i).
I have both flats and bowls and vastly prefer the flats. Not only do I find them more comfortable but the change to the sound is just more preferrable - there's a touch more mid-range but the added mid-bass balances better against the treble with the flats.
I'll go into sonic details at a later point in time but there are a few things I want to say now. First, the RS1 is the first
headphone I've heard that actually captures a violinist's vibrato realistically! I was stunned. I rarely listen to classical but decided to throw some on anyway (just to hear what the RS1 would do) and at first I wasn't even sure what was going on, I thought it was some kind of weird warble. Then I realized it was actually vibrato, wow! The HD650, K701, and AD2000 could never do this, I'm impressed. This makes me want to listen to classical more often.
Second, this headphone is surprisingly interconnect-dependent. Last time I heard an RS1 the ICs were the Audio Art IC-3 which were still burning in. Switching to my Signal Cable Silver Res Analog is a total sonic shift, and I do prefer it with the Signal Cable - more clarity, speedier transients, greater dynamics.
Third, while the Gilmore Lite probably wouldn't be an ideal sonic pairing for it for most people, I find myself preferring it - it increases the PRAT and energy to an addictive level!
And fourth, this headphone is the most ideal I've heard yet for Alison Krauss' music! Union Station has never sounded better - the banjo, guitar, and acoustic bass sound so alive and real, and the RS1 draws out every quick line.
I wasn't planning on keeping these, as the main reason I bought these was for a very temporary situation, but listening to these is making me want to keep them...