Enjoying my lurk immensely. If it's any consolation, Psychic and I are getting info from someone in a position to know that the platters of our beloved SL1200's (of which the platter is my least-beloved part, for its resonance) have lately begun arriving in a 'non-flat' condition (yeah, they don't cost what audiophile TT's do, and also use a compliant damping mat, but our sort always likes to brag on the 70's-era Nipponese mass-market quality angle :-) Well, I got inspired by Patrick and went down and took a 7" aluminum architectural scale to mine ('83 vintage), and you know what? Approx. 1/64" uniform deviation. I think it's dished, and I think they knew what they were doing.
Jphii: I've got all kinds of radical ideas for a TT design - just don't know how to implement any of them or how well they'd work. Send me a million bucks and I'll be happy to share. ;^)
FWIW: Personally, I don't really see *slight* deviations from perfect platter flatness as ever presenting an audible problem, and if a wood platter sounded best, I wouldn't be scared to get it. IMO though, if one isn't clamping and using a mat anyway, the deviations inherent in the record will make this whole question nothing more than an academic point of aesthetics. (Sorry Focusedfx, but that's based on absolutely no personal Teres experience whatsoever, which will be my reason for making like Tom and receding back into the 'woodwork' now...)