So I just took delivery of my O2 mk1 on Friday.
Wow, what a great headphone, there is still the inherent headphone limitation of poor depth, but the imaging and soundstaging is superb. Much better than my hd800 and, I have to say, much wider.
Also, it doesnt have the big hole in the mid range that is present on the hd800.
The only problem I have with them at the moment is that my ampflication is limiting the stax. I have a highamp design stax amp, and while it was great for other stax headphones, there just isnt enough gain or power for the O2's, they sound horribly cramp and congested on anything but the highest volume setting. I will try up the gain on the amp and hopefully that will set me straight, otherwise, looks like I'll be trying to build one of KG's designs, or saving pennies for a BHSE from headamp.
Hens