Pros: Very confortable, great bass, very light weight
Cons: You might need some equalization, mids a bit recessed
I must say that this headphones are very beautiful, the quality begins with the soft leather case that contains them. Once you open it, the blue color stands out but the real excitement comes when you lift them, they are extremely light and the headband has a very soft leather cover, the velour in the pads si very comfortable. The DT990 have a circular shape, so if you're used to a more elliptical headphone you'll notice a less "intrusive" shape, you'll get used to it very fast.
The sound is great, the bass is deep and the highs are very bright, some people find that kind of harsh, but very suitable for electronic, rock and some jazz, you should need some equalization for classical. On the other hand some male voices seem a little recessed, but not too much. The detail is amazing, the bass response doesn't covers the subtle details, you can spot very small details with them. I would tell this headphones are a little bit warm mainly because of the bass response, but very suitable for most music styles.
My recommendation is to take a listen to this headphones, specially if you are on portable sources or laptops I highly recommend to use an amp to really get the bass tight.