I recently bought these as well. I'm very impressed, I think it is about on the same level as the KRK KNS 8400 value-wise. The bass is very well done, it is so physical and impactful without affecting the mids and treble all that much. I actually find these to be somewhat bright (well, probably neutral is a better word) after getting used to the physical bass impact. I'm using the 770 pads with them and they alter the sound slightly, by giving the treble a little more sparkle. The change is not huge but it is actually a subtle improvement that improves the neutrality of this otherwise quite bass-heavy can. The 770 pads balance them out just enough, without losing the cool bass.
I bought them after also trying the Shure SRH940 and Ultrasone PRO 900. I can honestly say I prefer the Q40 over these much more expensive headphones. It doesn't have any glaring faults like those two high-end closed monitors. It handles pretty much all music styles well and it is not fatiguing to listen to. Great stuff. My only concern is build quality - that tiny little exposed cable is a very bad design decision (although it looks somewhat cool in a retro way).