Took a quick spin with this. Popped over to the Wawnet Inn, and was unable to move once inside. Some structures of some kind were blocking the door, and when I TCL'd through, there were rocks and trees inside.
Went to go see what it did for the manor in AFK_Weye, and for some very strange reason entering the manor caused a quest stage in AFK_Weye to update long before it should have been possible for it to happen. It also dropped several statics inside the manor - fences, a building, and several rocks and trees. The middle and upper floors had similar stuff, looked like probably in the same locations as downstairs.
Every interior was forcing some kind of strange white fog weather as well.
I'll grab some screens in a bit here to show. This all happened with the 0.91 update.
Ok, screenshots:
http://img4.imageshack.us/img4/5359/screenshot801k.jpg - I circled the rock in the corner since it's supposed to be outside the building. The wooden beams overhead seemed awfully low to the ground until I realized what happened. The building's own exterior mesh was copied into the cell with everything else. Though you can't see it, the two NPCs at the table are actually trapped on the outside of the exterior mesh wall.
http://img202.imageshack.us/img202/4919/screenshot802s.jpg is another shot inside the Wawnet Inn showing the beams coming down far enough to block access to the door and the upstairs level.
http://img249.imageshack.us/i/screenshot803.jpg/ - I TCL'd outside the wall to get a look at what was outside. That farmhouse and several miscellaneous items embedded into the big manor house should not be there. It seems items are being placed without regard to weather the exterior items have been disabled.
http://img130.imageshack.us/i/screenshot804q.jpg/ - Inside the manor house, with a different farmhouse that shouldn't be there. That one is from outside the building, it's next door. This also shows the white fog. That big light next to the door, I have no idea where it came from.
Also, while TCL'ing in the cell, if I went up high enough the landscape that should be visible underneath the objects is there. It just seems to have been placed too high. Also saw some missing mesh icons scattered about.
It looks over all like this system is a huge success as long as the disabled items can be handled and a cell's own exterior mesh isn't placed in the interior. Though I'd have no idea how you'd single it out.