RPP You may use it without Photoshop, but main idea behind this applications is conversion quality and most likely you will need additional tools like Photoshop to at least apply some unsharp mask.
Give it a try If for some reason you don't like conversion quality of existing RAW converters, you want to squeeze everything out of your RAW files, you want to process some heavily underexposed images and see those details in shadows instead of black digital void or you just missing that old slide film look in your digital camera.
(Version 3.4.6)