Thanks for the replies everyone. Hopefully there will be a pair available to demo at the upcoming meet here in Chicago, so I really don't expect to be purchasing anything until then. I'm always happy to hear other's experiences, though.
I am also a fan of trying it before you buy. What parts of your 650 do you love? The LCD is going to be totally different.
What are your favorite genres of music?
Hard to say what I love about it really without comparing it to some other headphones I have owned, particularly the Grado 325is and Beyerdynamic DT 880. I guess the first thing is how full, rich, and thick the 650 compares to the other two. I love that it is comfortable and has a non-fatiguing sound signature. I think it sounds more intimate and warm than the 325 and DT 880, very engaging. The soundstage seems very good to me, which I enjoy. I didn't like the DT 880's because they sounded too clinical to me, a bit boring.
Sometimes I wish there was a little more detail with the HD 650's (but who doesn't want more detail?), maybe a little more separation or air between the instruments in comparison to the HD 800, which I recently listened to (although I found the 800 a little more on the analytical side of things). Sometimes I miss that crunch you get with the 325is on hard rock, but I guess you can't have everything.
My favorite genres of music are rock, pop, indie, and jazz.
Oh, and regarding music, I have recently began purchasing CD's again for the quality, so I'm definitely making an investment there. And of course I'm always discovering new music (aren't we all?), so for that I use Spotify more.