Generally, and quite most of the time, I find that Costco scans can be used as-is. I don’t like spending time on the computer doing Photoshop or Capture NX trying to fix a digital image. However, I’ve found that scanner manufacture and operator settings can result in different interpretations of one’s film. Using a different scanner for a particular effect should be a matter of choice. For reference here is a comparison of three different scanner’s, Noritsu (Costco), Fuji (Longs Drugs), and Nikon 9000ED and their results of scanning Portra 160, 35mm film (click on Flickr link below)*:
http://www.flickr.com/photos/hawaiiankava/5935592269/in/set-72157627202248584/lightbox/
There are perhaps three ways of looking at this: (1) the facts that there are so many interpretations can be unsettling to some as a lack of consistency in scanning services; (2) reasoned choices or calls for adjustment can be made for suitable results; and, (3) this is an indication of the richness of film to allow for masterpiece or mess-up or on average a very acceptable result. Film is rich because it allows a lot of options for interpretation.
Here is another example of both scanning differences and the same information-rich film negative captured with an M3, 15mm Heliar and Ektar 100:
Longs Drugs Moiliili scan http://www.flickr.com/photos/hawaiiankava/11113201024/in/photostream/
Nikon 9000ED scan http://www.flickr.com/photos/hawaiiankava/11114061343/in/photostream/
*The image was captured on a Leica M6 (chrome) with 50mm Summilux ASPH, handheld.