I've been using it in beta for the past 2-3 months or so on my windows pc, and it's been excellent in terms of functionality and customization. Twice, I started up a game, and Steam immediately notified me that game capture ran into a problem and isn't recording (resolved by just restarting the game). Other than that non-issue, it's been perfect.
Anyway, was very happy to replace the nvidia spyware with something that works. I'd still feel better about a FOSS alternative for screen capture though. Anyone have a suggestion? The handful I've tried weren't working out.