The short version of this review is that I am 100%, absolutely pleased with these headphones and would buy them again.The long -What do I like?Sound - Pristine reproduction, almost completely uncolored. Pure, clean bass and excellent sound imaging. Instrument / performer location is nearly transparent with these, creating a wide soundstage. A great test album for these 'phones is the Bill Evans Trio album "Exporations". "Nardis", "Israel" and "Elsa" feature some very low acoustic bass from Scott LaFaro and very delicate brush work on the drums. These are the first headphones that I have heard that reproduce this so well. Classical music sounds excellent as well - John Eliot Gardiner's recording of Beethoven's Symphonies on period instruments is ridiculous on these. It sounds so good! Modern rock is also handled with ease - uncolored and clear. Perfect bass response, and when you want a boost in the bass, the DT990s handle the extra kick easily. I used the EQ on my headphone amp to boost the bass as a test, and found no problems or muddiness. IMHO, these phone do not need the bass boosted - they sound great with no EQ.Comfort - The most comfortable headphones I have worn. I don't think there is any problem here for anyone.Construction - Okay, these are only a few weeks old. I cannot attest to the long-term durability. I can say that they appear ot built very well. The cord is heavy and appears to be durable. The constuction is solid, yet lightweight. I think it'll do just fine over time.Comparison - I do NOT own 43 different pairs of expensive headphones. (As it seems many reviewers claim to own!) I have one other pair of "real" headphones; Grado mid-priced (~$100) headphones that sound great as well. The DT 990 kills them, leaves them in the dust so to speak - as they should for the price difference! (But I still love the Grados!) What I was able to do a few months ago was visit this absurd electrincs shop in Tokyo (Akihabara) and audition a ton of 'phones with my own MP3 files. The DT 900s were among them. The only headphones that I thought were this good were the Sennheiser's with "wood-trim" and the DT 880. (Sorry, I forgot the model number of the Sennheiser) I cannot give you a run-down of this model compared to that model ad infinitum. The DT 990s sounded better (to me) than many 'phones costing quite a bit more - some AKGs (I think the Quincy Jones model) and Audio Technica were hundreds more expensive and IMHO were inferior to these. I can tell you that I love the sound of these and do not regret buying them.I am not going to comment on noise isolation. These are open type 'phones, as anyone intelligent enough to read has already discovered in the product description. If you are reading this and don't know what that means, do an internet search on that term.Plus that, they are GERMAN made and engineered! (If you don't know it by now, literally every product made in Germany is superior to similar products made elsewhere with one exception - dental floss.) This product again reinforces my admiration for German engineering. Simply awesome product!I hope that this review helps you to decide what to buy. I had a very difficult time deciding, and had the good fortune of being able to visit Tokyo prior to buying. I was able to audition dozens of headphones in a store there, Akihabara. I don't think that you will find that here in the US. (If there was a store like that here, all of the audition headphones would either be broken or stolen, sadly.)Update - December 30, 2012 -Fantastic 'phones!!!! I am fully aware that nearly all headphones exhibit some type of "break-in" where the audio qualities may change slightly after some hours of use. I can only say that the Beyerdynamics sound better to me than they did a month ago. Hard to qualify that, really... I think that they sound more "open" and transparent. Excellent 'phones, no change in my opinion from earlier. Just a very fine audio product and the best headphones I have heard. Easily in the category of "Would buy again."Update - January 2014 -Better than ever - cannot knock these at all. Worth the money, sound great, look and feel as good as the day they were new. Sound better than new. Very happy with these after living with them a bit now...I recently bought the much cheaper Bro' of these Beyerdynamic DTX 910 Stereo Headphones for Portable and Home usage (Silver Black) for use away from home, and am very pleased with those for $70.