They're buggy and unreliable, and often slow. I'm on a Mac. They're good when they work but they just aren't ready for primetime. Ok, I might be picky, but I have been a photographer for almost 30 years and I invest in tools for long periods, like I'll want ten years of use from a camera, and I'll want an investment in learning software to pay off. I wish that a lot of the FOSS tools actually focused on UX and what users really need.