just to chime in, I used Iview for many years on a Dell. The feature I used extensively was virtual catalogs - essentially creating a new folder of images from the existing ones by tagging them. It worked ok in iview but was slow navigating around. Since using PM, I have stopped using ivew and found it quicker to find and group the new collections by actually copying the images to a new folder using PM. I know this isn't the best way to organize since I now having multiple copies of images in multiple folders but it's faster to work in the PM interface then iview.
I also eagerly await the catalog feature.
David