I have owned mine since they first came out. For many of us coming off of Carbines and Walkabouts the D-800 is inherently a little warmer sounding which many of us refer to as darker. IMO it's not a limitation or issue, more of a comparative statement. I also owned GK heads and still have my GK MBs. Once again they are a bit brighter with EQ controls set at noon.
I'm a finger style player with big hands and find plenty of top end in the D-800 using the head's tone controls. I think that because the head only has a deep switch (no bright switch) and the mid EQ points are a little lower (but very nicely chosen) than on many heads, it tends to give the impression that it is only focussed on lows and lower mids (i.e. being darker sounding).
FWIW, the unusual mid EQ points were chosen by players in blind experimentation and not even Andy knew the specific frequencies until the testing was done. It's true that the follow on Subway heads are a bit brighter/more inherently open up top (to varying degrees), but the EQ on the D-800 should get most players pretty much everything they'd want.
The fact that I still own and like my D-800 with all the other SW heads I have can rightfully be interpreted as meaning I don't see it as limited in voicing. One last thing that I have always enjoyed about that head is how live performance freindly the simple but effective control set and features are.
I hope that helps, and as always, we all hear things differently and have different tone goals.
