I'll make this a short review and just make several points.
 
- Excellent unit for beginners. You can use it so many ways, it's really an all-in-one.
- Build quality is great, I haven't heard of any dead units. Some minor problems here and there but they are quickly resolved.
- Superb support from the company. Fast and helpful emails.
- Upgrade and resale potential. You can use this as a DAC and amp and down the road get a nice tube amp hooked up to the tube pre-amp outputs on this device. Swapping the tube and opamps also upgrades the unit. I think resale value should be good due to the flexibility of the unit.
- I'm not disappointed with the sound quality of the unit but I only have a $60 portable cmoy amp and a computer sound card to compare it to.
 
Bottom line is it's an excellent product for the money backed by some of the best customer support I've seen from a company.

These headphones are my first pair of high-end (probably mid-fi to some) cans and after a year or two of use, I have mixed feelings about them. When I first got them, of course they were a HUGE step up and I loved the bass from them, they were the perfect headphones to me. I was hearing sounds I had never heard before in music, hearing imperfections and low-quality sounds as well. However, one thing I've learned on this site and in time with various equipment, terms like "quality" are largely based upon a users' prior experience with other products. I went from some really terrible $20 and $30 over the ear headphones that were just "ok". The jump to these cans was tremendous.
 
However, after learning more and being able to nit-pick "quality", I think there's quite a bit of room for improvement. A few things in this area would be sibilance (I think it's called) where the higher sss sounds, sound like they were encoded at 64kbps or something. While this isn't hugely noticeable, it can get annoying if you really listen for it. Another thing would be driver distortion, sometimes the driver can get contaminates on it which can ruin the lower frequencies. From reviews and posts though, there almost seems to be a defect in some drivers where no matter how much people clean, it never goes away. I find that usually, for me, cleaning does help. Typically some low-strength tape works such as painters tape, getting around the black foam and whatnot.
 
While there are those downsides, I still fully enjoy these cans. I'm happy with what I paid and how much use I've gotten out of them and will still continue to get out of them. I don't know that I would recommend them to a mid-fi user but someone that is just beginning to get into quality audio and likes gaming or movies, this is an excellent pair of headphones. There are also plenty of mods to these cans to help improve the quality and if you really like the style but want something better, there's the DT880 or DT990 models that are more expensive but you do get more.