Craig,

Yes I have noticed this myself - but in a different way. You were talking about the RAM retaining the value over night. I have seen certain ram locations powering with a specific value whenever they are powered up - I always used to wonder how that was possible !! Not that they had back up of any sort - intentional or otherwise.

Anyway till date I have believed in the following dictum ( from the data shet of Philips 89c51rx2 )

Reset redefines all the SFRs but does not change the
on-chip RAM.

And till date have not had any problem because of the belief.

Raghu