The improvements listed:
What is new/Content Description
Support for the D50 has been added.
Chromatic aberration control option has been added to the "Image" menu (available only with digital SLR camera RAW images).
The Red Eye Correction feature included in Nikon View and PictureProject has been added.
A Performance tab has been added to the Tools / Options... menu.
Correction of other known issues. I wonder what the "other known issues" are?
Somebody please tell me that they've improved performance on the MAC. The other 'improvements' are meaningless to me unless I can actually load and use this program. I had to remove 4.2 from my Mac because in interfered with Dreamweaver's anti-pirack code. (with NC4 installed, Dreamweaver wanted me to input the security code each time it booted)
Both Nikon and Macromedia pointed fingers at each other (sound familiar?)