That may be true with early adopters of the V1 650, but times have changed a bit. It seems it has, especially with the revised current drivers and along with a greater selection of HQ amps available today, increased it versatilty noticeably. 650s are much more respected today, than in its introduction and its subsequent revision model.
Probably true. I personally don't feel a treble lack in the 650, at least with aftermarket silver cables. The 650 can reproduce the blare and blat of brass instruments with the best of them, better even--going by some comments--than the LCD-2. This also replies to Roger Strummer's post above--I'm no longer sure that the 650 has "warm non-offensive sound", intentional or not. (Those comments were of course written for the original 650). I'm not even sure the 650s FR is "a deviation from Senn's ideal flat frequency response". The 650 sounds flat to me, and according to HeadRoom's description of the ideal response for subjective flatness (increased bass, falling treble above 1khz), is just about right. Other FR graphs, one published here, show an even flatter response than HeadRoom's--and amazingly, flatter than all the current flagships!!.