Well-structured Legacy Content

A prerequisite for a successful import is that the legacy format is fairly well-structured. It should also be noted that if you're moving from unstructured and non-topic-based content (such as Word), you are likely to want to rewrite quite a bit of the content to make it topic-based, reusable, and so on. So while the import functionality works very well, you should always consider carefully what is the best strategy for your content.

If your content is well-structured and divided into topic-like sections already, you may gain a lot from an import, saving you time on migration. But if a lot of rewriting is necessary anyway, the gains will be smaller, and importing in such a case might not even be a good idea at all.