Hi CyberBob,
Yup, anyone w/ a free account can create up to 5 private maps (unlisted or invite only) maps. Keep in mind, that you can now create as many public readonly maps as you want if you don't mind someone seeing your shopping list, for example, or your notes from physics class but you just don't want other people to touch them.
If you had 15 unlisted maps from before, they are grandfathered in and don't count toward your 5 private maps.
We agree it would be nice to add a group of collaborators, why don't you post that to our user voice forum so other users can vote on that idea!
http://maptini.uservoice.com/
Thanks for using the app!