I really love it, of course, but I don't think it's supposed to work this way.
Before I exit the game, I select Shift+F4.
Then when I re-enter the game, I have Full Detail plus the Ground Detail and I can see the trees at least twice as far as without this setup. The terrain just looks much better to me, and yes, it costs me ~20% of my frame rates.
I'm hoping this can be a deliberate setting, such as a check box. If it already is, I'd like to know, after all, some day I'll have a machine capable of handling it all lol.
Figured I'd better post it in case this is causing others a problem.