Pros: Comfort, Build Quality, Detail
Cons: Open back lets in noise, after hearing them with an amp. you'll have to drop another $300+
Just got a pair of these for Christmas and have to say that I was very impressed with the box they came in, very solid packaging, and neatly organized cord. There is a 3.5mm adapter included in the box, something I was not used to coming from a pair of Grado SR225i cans.
The build quality is very good, I don't feel like I will scratch or dent them without a decently high tumble. The cord is detachable and feels like it will not likely give out anytime soon.
As for comfort, I never really found my old Grados that uncomfortable (I know you guys/gals on Head-fi and reviews on Amazon always talk about Grados being uncomfortable) but now I can hardly wear them after having used the HD 650s. It is a very comfortable fit once you get them adjusted nicely to your head.
As for sound quality, I play everything in FLAC or MP3 @ 320kps using Foobar2000 with the kernel streaming plugin.
Due to the fact I don't have my Maverick Audio TubeMagic D1 Plus Edition in yet, I have been trying to use the 3.5mm jack from my laptop to listen to music. The HD 650s don't sound very special through that source at all, they are very boring when plugged up to my android phone as well. I almost picked up my Grados again just until my amp came in, but I just like the feel of the HD 650s so much more.
I eventually used HDMI out from my laptop to my harman/kardon AV receiver along with Foobar2000 w/ WASAPI (manually selecting the receiver in the output list) and plugging my headphones into it as a source. This made the headphones sound much more worth their money and really blew me away.
Music I tested included Pink Floyd, The Beatles, Led Zeppelin, Daft Punk, OutKast, The Chemical Brothers, Kanye West, and Fleetwood Mac. I heard details in Time by Pink Floyd I have never noticed before.
I am very excited to get my Maverick Audio TubeMagic D1 Plus Edition in. My library is waiting for me to listen to everything over again.
If anyone wishes me to report in how the D1 sounds as a source for these cans let me know in the comments.