It is, at the least, much more aggressive than it was. Standing on a building and looking out across Morris I see red. Lots of red. And it's not the bad kind you see when you're angry, it's the good kind when you turn octree rendering on and see culled areas. It looks like the whole of the ground is culled, as well as very small octree cubes obscured by the ramparts of this structure I'm standing on. It truly makes me happy to see this, and what's more it greatly improves my frame rate.
It looks as though the octree cubes no longer form as static cubes stacked within each other, but now form around groups of objects, constantly reshaping as very active objects move about. I feel this is a good change for SL, as it will allow the hiding of objects even in an outdoors area. Nexus Prime in Gibson now shows as smoothly as Morris does for me from the outside, which means the culling of objects in very large spaces hidden from view also seem to be working.
I noticed a glitch though when entering the structure of Nexus Prime and worked my way North towards Bonifacio, the entire sim North of me was culled! Though I could see open areas ahead, nothing of that sim would render until I crossed into it. It was as though it was a vacant lot (with nothing but the ground rendered). I imagine it has something to do with the sim previously being culled while looking at the outer walls of the structure, and then not checking to see if it should be rendered again in a timely fashion (though 20 seconds seems a bit much, that's how long I took to realize the fault and explore into the culled area). Also, kudos on Nexus Prime Bonifacio being smoother than ever as well. I can spin and get a consistant 8-11 fps (as opposed to a previous 2-5 fps, a definant improvement).
I can't really think of a better way to do the occlusion culling, but if I get any ideas I'll be sure to post them. Looks like it's ready for prime time to me.