In Nautilus 2.x it was very easy to open any file using a specific command like your own program or script. The »open with« dialogue provided a field to type in a custom-made command.
In Nautlius 3.x this does not exist any more. But in place of it you find a complete useless button to search the internet for programs to open your file.
This interferes with all-day work because now the only way to open an file with a non listed application is to create in desktop-file. That's an unacceptable and very Windows like behaviour.