I had a chance to test a device today. I brought 2 headsets/earbuds (Sennheiser IE7 "16ohm" and beyerdynamic 770DT pro "80ohm"). I also tested the phone with the earbuds that come with the phone and two headsets that were at the place where i tested (one AKG and one other something. I did not find out the ohm on these).
Unlike everyone else I did NOT notice a huge difference between low ohm and high ohm headphones. The poor bass-response was present either way. However, the sound DOES get better overall. I should note that i only had a chance to test mix-radio, and streaming music is never as good as lossless (is the lumia 800 able to play uncompressed files?).
It sounded to me that the main problems were below 100hz. The bass- and kickdrum-response was almost completely gone (20-80hz) and the fatness in the bass was, well.. NOT fatness. However, the sound has a thickness to it, which would suggest that it has quite a lot going on between 100hz and 300hz and I suggest that this thickness is the reason why so many people are not outraged by this. Also the fact that many low-end headphones have bass and treble boost to give a more hi-fi sound often gives a misleading sound. If not downright ugly sound, no matter what the device (phone) is outputing. People get used to this.
I will not be able to use Lumia 800 as a referance device for music and sound mixes, but I ordered one anyway. Damn nice phone. 
I hope they add EQ quickly. And if they can: Get the bass-response sorted out. This problem is found in ALL Lumia 800 devices. No reason for Nokia not to deal will this full force.
