I would really like to see the ability to create invidual accounts en mass in SiteCatalyst. This could be something as simple as uploading a CSV file with name, email addresses and randomly generated password.
I'd suggest to look into the API for that. I use it and it's a huge time saver. If you don't want to code scripts, you can simply use the API Explorer to execute the API calls.
One of our engineers in San Diego contributed an Excel client plugin that interacts with the SiteCatalyst Admin API. It could be used to manage large numbers of users.