Pros:  The comparator, for one. Not just it is there, but also the way it has been implemented, permitting overlaying one image with the other for easy comparison of small detail. Other than that, there are too many features to list. I can't imagine what else one could possibly want, except...

Cons:  No TRUE color management. i.e., custom ICC monitor profiles are not supported.

Other Thoughts:  What a thoughtful design! For most users (i.e. those not using custom monitor profiles), this should rate 6 out of 5 stars. This is an incredibly full featured application, with easy, convenient access to just about anything you could possible expect. Though shortcut keys are not customizable, they are so well chosen that this is not at all a problem for me. The only other thing worth mentioning is that although browsing speed is excellent for JPEGs, it could be improved for RAW files, which tend to load slower, by using a look-ahead concept.