I've had all 3 incarnations from the original to now the blue dot.
As far as difference in sound quality, the blue dot is better across the board with one major possible reservation. For 2 channel, the problem with squashing details, hardness in the mids, lack of soundstage and loss of recording ambience has all been very satisfactorily eliminated. I was really amazed.
My major reservation is that as with all new 950's mine sounds overly bright and fatiguing on the high end. All my others became very neutral sounding after burn-in. But so far I've had the blue dot in my system for 3 weeks of admittedly sporadic use and it still sounds very bright.
Fortunately several others with blue dot units commented that the burn in process did take longer than with previous 950's. And if it does, as I expect it will, the blue dot would be a very big upgrade in sound quality - especially in 2 channel.
I really stopped listening to music on my earlier 950, but even with its bright presentation I found the blue dot to actually be quite musical and involving in 2 channel (something I never thought I'd say). I actually spent time re-discovering some of my older recordings.
But I'm waiting for the burn in to be complete before I really spend much time with music on the blue dot. The brightness IS fatiguing for now.
[This message has been edited by HT crazed (edited February 21, 2003).]