I have used the nightlies since starting with the first Gotham Beta. All works very nice except: After you install it over a Frodo install, all your installed add ons should work. But after you install it many of the add ons that were not already installed will show as incompatible.
So my advice would be to install all the add ons you like and then install Gotham over the frodo install and it works fine. Can't really lose because if you do not like it, just install Frodo over the top and yu are back where you started.
Gotham is on the edge from being Beta to going to General availability imo, the android version is working well on my tablet it feels a lot faster, I am able to watch things that were struggling before with Frodo.
There are a few add-ons that are incompatible with Gotham no big problem most of them I have never used