I'm so happy I found this. Xon has so many awesome AddOns. This one, paired with the Custom User field AddOn is key to my forum. I can use custom fields to allow users to self-join certain groups and then set up a Promotion based on user selection. This AddOn allows the selection process to happen instantly upon save instead of waiting for the hourly cron job.
If you don't have this plugin, get it. Because the struggle with user group promotions syncing actually makes me want to pull my hair out. For users who used to use Join User Groups by ThemeHouse this is exactly what you're looking for. Honestly not that I'm encouraging it but I'd pay for this plugin. If you have an extra few dollars to send Xon please do to assist them in keeping this plugin up-to-date.
I should have rated this addon earlier as I could not live without this addon and it deserves every praise. As the other reviewer says, this should really be in the core. XF user promotions system is flawed in my opinion, as changes don't take effect immediately, because the it waits the cron to be run, which at best runs every minute. So, users make changes in their profiles using custom fields for example, and when saved, they don't see the effect of it. That confuses the users as it is very counter-intuitive without this addon. This addon makes the changes immediately effective. If you are using custom fields, you won't be able to live without this addon. Thank you.
This is such a critical addon. I think it should be core functionality. Thank goodness Xon came through again! I use this for a lot of my user custom settings. For example, I have a custom user field where members decide whether they want to see a list of new posts in the thread view side bar. Depending on their answer, they have a promotion to a user group. Because of this addon, their settings change takes effect immediately, and I don't get PMs asking why it isn't working. Such a time saver!