For 9 months I have been using RapidRaw as part of my RAW image processing workflow. So much so that Rawtherapee and Lightroom have fallen by the wayside.
Described perfectly as "A beautiful, non-destructive, and GPU-accelerated RAW image editor built with performance in mind." I have seen the improvements and enhancements over the past months and the developer, Timon Käch, deserves much praise.
It's free software so if you find this useful please consider contributing to the work.