It destroys the original file if converting failed.
A typical Sourceforge project in that after the initial release it is abandoned for years. After 5 years this program needs to be updated to support .NET 4. We can't keep putting every version of .NET on our PCs to support programs that ought to have been updated by their developers.
Small download (not bundling some old ffmpeg version like many others), nice clean UI, plenty of presets. What it's missing is option to split video files (without re-encoding). If splitting was added to it I'd say it's the best GUI for ffmpeg.