I just can't see it being a disc error (in fact I would place a large bet on this!).
Discs are uniformally printed based on the v1.0 vanilla version of the game. Its almost certainly personal hardware and system set up.
I'm now sure i had a faulty disc!
I went to the store where i bought the game and explained my issue.
The storekeeper made some calls and took my disc back and replaced it with a new copy.
Just got home, deleted all Skyrim installed data and inserted the new gamedisc.
Installed the game again and installed the patch again.
Loaded my save from earlier where i could not exit the Abandoned Shack from the Dark Brotherhood quest because the world was missing and crashed my PS3.
I now can exit the Shack, the world is fully there, no lag, no hickups, no stuttering... everything runs perfectly now!
So there ARE faulty discs out there for PS3!