I never used ICEFS on the system partition because AFAIK MOS cannot boot that filesystem. I always used ICEFS for normal file storage. All kind of files: installed programs, music, text, pictures, mail postboxes, system backup etc. Maybe if you only use it for large files it works better. I never tried that because it should behave the same for all kind of files. And if you need to run the ICEFS doctor tool that often because the filesystem can make trouble then the filesystem is not really promising to give him my data.