I am going to migrate 5 WP blogs to WPMU, as it is difficult to manage that many different blogs (updates, maintenance, ect..) and I have several more that I may be managing in the near future. I am new to WPMU and have a questions about how to make sure all the register users of the blogs get imported into WPMU.
Note: This is really only an issue with two existing blogs (others are low volume sites).
Going through the XML export of one of the blogs, I can not see how register users are "imported" into the db. Is there some way to import the registered users? I don't want to ask several hundred users to "re-register".
Could this be done with multiple DBs or is there an "advanced" import function I am just not finding? Documentation would be worderful, if it exists.