I've used PhotoReviewer for a couple of weeks now. I typically capture several hundred (200 - 600) raw image files from my Canon 1Ds or Canon 10D. Although I "process" the images in the commercial software program Capture 1 DSLR from Phase One, I do my initial edits ("approved" or "vetoed") in PhotoReviewer. It is designed to do just one thing well: edit your photos by moving the files from the capture folder to either an "Approved" folder or a "Vetoed" folder.
PhotoReviewer is much faster at viewing the images and moving them to an approved or vetoed folder than either Capture 1 or Photoshop (using the file browser). If you have hundreds of image files to edit after every shoot, this program does just that very quickly and very well.
The program lets you allocate as much memory as you may need to pre-load the images so that as you move through the queue each image loads instantly. This pre-load is done in the background and works fairly fast.
When I use PhotoReviewer, I am mowing through raw camera files of 6 to 11 MB. If I am editing quickly, then I can "hit the pre-load buffer" and I must wait for the next image to load (when working with JPEGs, I cannot reach the end of the file buffer). When more memory is allocated, it takes even longer to hit the buffer, if at all. Using a 17" PowerBook with 2GB RAM, I allocated 1GB to PhotoReviewer for quickest editing. Make sure you understand the preferences well before you change any of the settings.
PhotoReviewer lets you rotate images, then move them from the current capture folder to either an "Approved" folder of your choice or a "Vetoed" folder of your choice. That's all it does, and it does it very well.
It's been the best $10 I've spent in software all year.