I’m not sure of the HDV world, but I’ve been using a Focus Enhancements FS-3 for years in FCP without any issues at all. It has worked everytime with no failures. The files import directly in with no issues and will play on the timeline without any further rendering.
As for importing HDV, I have no eaperience at all. HD Cam yes, HDV no. Have you tried posting this over on the Firestore forum?
Tom