Registering users through Joomla

I use CB with JReviews, which allows guests to write reviews and register on the same form. This is a very convenient feature, but the registration goes thru Joomla, not CB.

I know, that all registrations should be done thru CB, but how can I take advantage of this very useful feature? Is the only problem with allowing such registration the need to sync users every time or there is something else too?

jReviews would need to have an integration for CB. They'd need to use CB API to store the user instead of Joomla when CB integration is enabled. Alternatively they could just redirect to CB registration. You can not use a registration other then CBs. Doing synchronize each time a user registers is not an acceptable option.