Duplicate NID + VIDs

From what I remember, there is a table which is updated with the most recent versions of NID and VID. The I/E UI, the script retrieved the relavent NID and VID and incrememented them before acting.

In my own efforts, I found that if you tried import duplicate NID and VIDs, it wouldn't work. Similarly, some content data types require different data definitions, which also affect what needs to be calculated before data is imported. This was handled automatically for the Drupal default content types, and some CCK types, but not all.

So the short answer is that if you are importing data and the content type is supported, just leave the NID blank, and it will be auto-incrememented when it is imported, if it's a supported content type. If not, build your own translation.