Updating a Users Join Date? I'm doing a big import of users from an EE install using the Import plugin. I can pull in all the details I need except the join date, so I looked at the craft db to see where it needs to be changed.

I successfully managed to change it by updating the craft_elements table, dateCreated column. This changed the join date in the control panel, however it does update the dateCreated column in the craft_users table so I updated there also. 

Just wondering if thats correct?
Yup, that's correct. The craft_elements.dateCreated column is the one that is referenced by the user's Join Date.

For the sake of being thorough, I prefer to copy that same value into craft_users.dateCreated, just as you have done.