For any professional level application, you''d probably be better off writing your own format. After all, you would know the types of models you need to store better than the creators of the .x filetype and could probably come up with a more efficient method. But .x is a good general purpose format. Real easy to use. Think of it as a honda accord. Good all around vehicle. But if you live in the mountains, you might want a jeep. If you need to go real fast, you might want a ferrari. If you''re an average family with average needs, the accord does everything you need it to.