Hi Alastair,


>Would a slower class card (but still >35MB/sec) be written
>to at the same speed?

I am not aware of any 35MB/sec. cards but the D700 writes to 45MB/sec. Cards
at between 27.2 and 28.9 MB/sec. Raw and 23.6 and 25.7MB/sec. Jpeg.

>I wouldn't be surprised if the 90MB/sec
>figure was an ideal and fastest possible speed achieved under
>laboratory conditions only; which would mean that say a
>40MB/sec card might reach 15MB/sec in normal D700 use. Hope
>that last bit makes sense.

While the maximum read and write speed is specified by the card manufacturer and the maximum speed of the fastest cards increases with time, the maximum write speed of any devise is fixed when it is manufactured. The fastest cards available when the D700 was introduced were 45MB/sec. I suspect that when the D700's buffer design was finalized, the fastest cards available were even slower.
Thus the maximum write speed for devises (cameras, etc...) will always lag behind the write speed of the fastest cards available at any given time.
Good Luck and Enjoy your Nikons!

Best Regards,
Marty