I've been following the Rachmaninoff CD thread with some interest.
I have a slightly different experience.

I have Wayne Stahnke's Disklavier version of the Rachmaninoff Ampico
rolls which includes "Prelude in C Sharp Minor", the corresponding
Ampico roll, and the Edison Diamond Disc as played by Rachmaninoff.

I find the timing and expression from record-to-roll-to-MIDI to be
spot on.

The hill-and-dale Diamond Disc recordings, in my opinion, have a much
truer sound than the laterally-cut 78-rpm recordings of the same era.
If there is enough interest, I could potentially record the Diamond
Disc performance into an MPEG3 file.

As for piano types I listened to, the Ampico was a Knabe (recently
sold), the PianoDisc is on a Knabe, and I would guess that Rachmaninoff
recorded on the Steinway A used at the Edison recording studio (another
piano that I was lucky enough to possess for sort time).

Regards,

Scott Currier
http://www.currierandives.com
http://www.worm-hole.net/members/scurrier