By now most of you on iOS should know there is a completely new version written from the ground up. If you already own the legacy app you can keep running it in parallel. Those that have purchased the app will have the base version subscription extended for up to 2 years depending on when you purchased the app.
For premium users there are 2 new map layers which are of great value. National Geographic maps (like the paper maps) and a brand new MVUM layer. Both require a premium subscription which is $29.99 per year.
If you have never tried Gaia you can now download the app for free. With this link you can extend the standard 7 day trial to one month for free. You should have to have your account setup prior to using the link.