I have On1, and it's decent, but, there is an unresolved problem with Pentax PEF files.
When you browse a folder, it initially shows all the images in the folder, but after a few minutes it filters out all PEF files.
Tiffs, jpegs etc are unaffected.
Whether it happens with other Raw filetypes I don't know as I have no way of testing.
TBF to On1 they did spend time trying to resolve but failed & offered a full refund, which I decided against in the hope the upcoming Photo Raw will solve.
There is a workaround by holding shift whilst starting Photo10 which deletes it's settings file, but obviously this may cause issues too, although I've not worked out what they might be yet.
This is on a Mac Mini 2.3 16gb i7 with PEF files from a Pentax K5