The LPs of this material sound good to great. I think I heard the old boxed set at my aunt's house - she's very hip - as well, and noticed no issues with sound on a good stereo.
To Steve's question, as I see it Blackwell definitely had more of a Max Roach thing going, melded with Afro-Caribbean rhythms, and that gives the music a slightly different flavor than what Higgins put forth (although I believe Higgins did take some lessons from Blackwell, to me he sounds a bit more like Kenny Clarke). They're both super clean drummers but with different kinds of clean. To me, however, what ultimately altered the movement of the quartet most was the revolving cast of bassists - Haden, LaFaro, Garrison, all very different. Surely someone has a better analysis than what I feel like typing up right now... calling ep1str0phy!
Listening to "Ramblin'" now and with all due respect to label owners and musicians on this board who've created some truly great art, it is also VERY hard for me to think of anything more musically perfect than this.