Because I don't know enough about Navision. I'll add it to my personal list.

Just a note, Navision is a product with great benefits, but rather difficult to really "grok" unless you're working with it in real life. It seems very popular for supply chain management in particular, though it's used for many other things. In many ways it's well designed, though a few VARs have taken it and built some extensions and add-ons that are, well, less attractive.