I’m afraid I’ve been using a 1.8 beta build of panda3d. I had some problems with 1.7x versions with my shaders. Try the online demo I listed on my website. My card is an ATI HD 3870 so its the same generation as yours.
My terrain is infinite and persistant as well. It is for the moment 100% procedural, though I have plans to allow height map editing later. Craig's system is supposed to be able to use modular tile bakeries and renderers interchangeably, but at the time I had a very hard time figuring out how to plug my system into it.
As for terrain collisions I haven’t really put any thought into it yet, but its something I would like to figure out as well. It can’t be that hard to feed the mesh into a physics engine… I hope.
By the way Craig’s geoclip engine is I believe still unfinished, but you might want to ask him yourself.