Groupjive new version

Hello.
As I read other forums here, new version of groupjive is under construction.
I would like to ask that if the transition between the current version to new one would be relatively easy for the end users (the users who actually create the groups and runs them). It appears that a lot of changes will be made to the new version.
I am going to launch a new website in a couple of weeks, it worries me a little that users can be confused by the changes.
It is a an option that I can hold off the group function when I launch the site and introduce it when the new version is released, but if the changes are not great for the users to create and run groups, then I would put the group menu in the site now.

It'll migrate existing GJ installs on install of the rewrite. It'll all be seamless and should require no further configuration after install. I don't know how long the rewrite will take so holding off on using it is entirely up to you, but it could be awhile. Review the below forge tickets to have an idea of what major changes are coming.

forge.joomlapolis.com/projects/groupjive/issues

The biggest major change is Nesting is being completely removed and frontend category management is being removed (categories will be backend managed only).

I have few main catgegories and many Sub-categories that are assigned to the main categories. I have 3 level category system.
When you mentioned "Nesting is being completely removed", I wonder how I can keep these category levels.

When nesting is removed your existing nested categories or groups will just automatically become top level. Meaning they just won't be nested anymore and behave like other parent categories or groups. There is no way to keep the nesting as it's being completely removed.