I used these, but not as a primary source for reviewing. These were nice to, as stated before, offer a clinical presentation to some otherwise obscure genetic diseases. Most people I spoke to who used UCV's, likewise, did not use them as a primary source. I think that the costs are a little outrageous, so if you can find used ones or even the previous edition (which I used), this should be sufficient.
If you buy the entire bundle of the new edition, you also get a free, otherwise unavailable color atlas. I checked this out from a colleague who bought this new series; my impression is that you probably do not need to buy this just to obtain this atlas book. (Apparently, this atlas is not for purchase from Blackwell Publishers unless you buy the whole set as a bundle.) Most of the images, including many high-yield pathology slides, are on par with the images in Robbins' Pathology.