Is there a good way to export a set of nodes from one Drupal installation, including node revision history, and then to merge these into another Drupal installation, including revision history?
I'm familiar with modules such as Node Export and Backup and Migrate... But Node Export doesn't preserve revision history, and Backup and Migrate doesn't allow merging (only full table replacement).
I've got a project called Import Merge I have been working that imports and merges Drupal objects of almost any type. So far I've got support for nodes and taxonomy terms included but the idea is to provide an interface for you to extend to any purpose you wish.
All you need to do is write a module that provides info to a few hooks and you should be able to save any data you wish. This project has not fully matured but works pretty well so far.
If you can export nodes to CSV then you should be OK.