Yes, it does. A teeny tiny bit. Usually it's not noticable, so if it is, you might want to check your capture settings. Even though it says "uncompressed" somewhere in the project settings, I don't think it's "true" uncompressed, which is so big it's ridiculous.
So unless you're using "true" uncompressed, every time you capture or export footage, you lose a generation. CineForm Aspect HD is great for multi-generation work. It uses a "visually lossless" codec. www.cineform.com
The capture window is generally not an accurate size for the footage, and it has to slightly resize for the pixel aspect ratio of your footage, so it is not a true judge of the quality. Neither if the Preview window, for the same reason. Rest assured, capture in the DV world is a simple file copy from the camera to computer, there is no margin for the quality to be reduced.
Export is a different story. Premiere has for along time had a default checkbox "Recompress" checked in the export settings. You need to uncheck this to ensure your DV does not get recompressed on export.
