Pros: natural bass, build quality, comfort, fast and detail, alike high end stats.
Cons: peaky treble, highs can be slightly bright on some tracks, paint chipping, may be expensive for some
The HD800's has been around a long time so I'm going to wrap up this review in a few paragraphs.
Having owned 3 HD800's at one stage, Serials 51**, 136** and Purrins 103**.
Going through all 3 before selling the first two and keeping only Purrins HD800 I bought off him, the early serial based HD800's are to my ears a bit more bass light and more warmer then my original serial 136** and purrins 103**.
I ended up selling mine and the early serial based HD800 and was thinking of selling purrins one due to moving onto speakers but I thought maybe I should keep it because its got the magical touch from purrin due to all the CSD plots he does LOL.
Anywho, the HD800 paired with my Beta22 amp sounds extremely good, revealing some detail that I've never heard from my tracks similar to the amount of revealing detail some Stax rigs I've auditioned and owned. Certain music can sound slightly too bright, some music with vocals can result in the voice sounding like it's pronouncing everything with a "Sssss".
Following the threads here or Innerfidelity (thanks to Tyll), performing the Anaxlius mod with a thicker but more denser felt material can fix the treble problems a bit, generally a bit of eq can fix this problem.
Most people say the HD800s are too bass light or no bass at all, but with proper amping, you can put on some bass heavy tracks and put your hands over the outside filter dome and you can really feel the bass vibrations. I actually gave the bass of the HD800's a pro because it actually sounds very natural, if I wanted bass, I'd just grab my LCD2's or some of my other bass heavy can's.
Surprisingly for a plastic build, it is surprisingly well built and durable, the only thing I can complain about it really is the paint chipping problems that people have, the silver paint really is prone to chipping off no matter how much care is taken with the headphones, which is why I'm in the process of repainting mine through a professional painting service, unfortunately I've emailed Colorware before to do a one off type of job and they said the reason they stopped the custom painting services through Colorware is due to warranty problems and modded headphones.
Other then that there really isn't anything else to say about these headphones, if there is one headphone you should try before moving onto high end electrostats it is the HD800's as there detail, accuracy and speed of its dynamics are similar to that of high end stats like the 007 MK 1/2's. etc.
Pair the HD800 with a top of the line solid state amp such as the Beta 22 and you will be wowing at every song you re-listen to that you've heard probably heard a hundred times.