There are no significant differences between 4.0x versions – the numbering changes are to identify builds to cover various manufacturing situations.

3.0 to 4.0 is a big change, 3.0 to 3.5 is a significant change, 3.0 to 3.1 is a small change. 4.0.1 to 4.0.9 is an insignificant change.

I won't be able to get the information on the CF cards until the New Year, so will answer them then if someone else has not.