I just purchased a Nikon d300s. I had a Nikon d50, Mac, iPhoto, CS3, and Camera Raw 18.104.22.168. With Nikon d50, no problem opening an image from iPhoto into Camera Raw/CS3. With the new D300s, the image opens into CS3 but does not open into Camera Raw. Do I have to buy CS4?
No, you do not have to. You can alternatively use the DNG Converter, which will process your D300S NEF files into DNG files, which can then be opened in CR 4.6 in CS3. The latest version of the DNG Converter, which supports the D300S, is currently in Release Candidate phase and is available here: