Editing Organazized has two great posts up with tips and tricks for getting the best-quality slowmo footage out of Final Cut Studio using Compressor. The first outlines the basic workflow, post #2 delves deeper into Compressor’s behavior at various retiming percentages and provides examples of the sort of results you can expect. In the footage for this example, best results degraded past 1/4 speed. At 25%, Compressor’s Optical Flow appears to preserve much more detail than what you can expect directly out of Final Cut Pro. Very informative articles.