(Still very much an amateur, and this is my first review, but I'll give it my best.)
So I grabbed the Shure SRH840 after a long trial and error process at Guitar Center back in December, and I've listened to them nearly every day since, for several hours at a time--so it's safe to say they're pretty burned in by now. Some background on my own biases: I like big closed cans, around the ear or on the ear, and listen to mostly rock music with them. After breaking my Audio Technicas, I needed to find a new pair of headphones that could work with rock music while giving a little bit of flavor. Basically, I wanted a pair of phones that wasn't "precise," but more "fun."
Comfort: 4.5 out of 5
They're definitely on the heavy side, but other than that, amazing in terms of comfort. I usually have my phones on for hours at a time--these are one of two pairs I own that don't hurt after a marathon. They have good enough clamp to let me move my head without them falling off (I have a very small head), but not so much that I get a headache. The ear pads are squishy pleather--padded and soft enough to not hurt the ears. The cord is long, but coiled, so it doesn't get in the way, but with enough length to let me move around. There's some moisture wicking fabric in the headband, which I imagine is a plus--but my head never really gets hot with headphones, so I can't attest to it.
Durability: 5 out of 5
Okay, this might be one of the coolest things about the 840. It comes with replacement ear pads, and a replacement cord. The cord itself is double-ended, and you have to plug it into the left-side ear (it locks into place, so it's not like you could yank it out by accident). I was really excited about this since, because of their weight, I was worried about the strain it would put on the cord. Although the cord itself is pretty tough--on the thicker side and coiled, which means it's less likely to feel stress to begin with. The actual cans themselves feel very durable because of their weight, and the band is some kind of flexible plastic surrounded by a thick, padded layer. And the ears fold up into the band, making them relatively easy to transport despite the size. Honestly, I put most of my things through hell, and I feel like I'd have to run these suckers over if I wanted to destroy them.
Isolation: 5 out of 5
What I'd expect out of a closed can, honestly. I can't hear much of what's going on around me, so there's not much ambient noise leaking through. As for noise leaking--I can pull these off my head, jack up the volume, and press the cups together (recreating the seal that's around my head, ideally) I can't hear a thing.
Sound: 3 out of 5
For full disclosure--when I test new headphones, I always use these three songs:
Okay, there's a few areas these cans really deliver in terms of sound. These phones really drive the mid-range--which is one of the things that makes them a fun listen, in my opinion. There's a lot of vibrancy and life in the sound, without being punchy. The mid- to low-bass is also crisp and well-developed without being rumbly or distorted; although I imagine these would leave something desired for a bass-fanatic. The sad part, and I think this is perhaps their biggest downfall, is that the high-bass range is really weak--perhaps the weakest part of the entire sound. I've heard others complain that these can become obnoxious with the high-range as well, and I didn't notice this until after they'd been burned in. The high-range is definitely on the sharp side, and on some songs it's annoying (pop lovers, beware!), but for the most part it blends well with the strong mid-range. As for depth, they're not flat. But they're not terribly deep, either. For the most part, the sound is all right in one spot, with slight variations. Honestly, there's a better soundstage on my cheap pair of Sennheisers. But for a simple rock experience--especially a standard four-or-five-piece band, Beatles-based rock, punk roots, etc.--you're going to have a great time. Long story short: I got my mom rocking out to the Offspring with these on. Overall, a fun sound--and totally an enjoyable pair--but the failures aren't just cracks, they're potholes. And that's rather disappointing for the price tag. If you can find these for $100 or less, I'd say go for it.
Overall: 3.5 out of 5
I do really like the 840. It's a good set, comfy, and for most of my music, it can really deliver. But like I said, for a $200 price tag (some places as high as $250!), they've got some pretty serious downfalls that I feel are inexcusable at that price range. I've seen them going for around $130 now (that seems much more reasonable), and for that price I would probably be a lot more forgiving. I've never heard another pair of Shures, so I'm not sure what the house sound is like, but, given my impression of the 840, I would hesitantly give them another shot.