In my opinion I think this was one idea they were right to change.
While throwing an old man down a lift shaft doesn't make up for a life largely devoted to evil, it is Vader's one redeeming act.
He steps in and saves his son when he could have hung on to a bit more life.
In the theatrical version Luke also does the right thing. By throwing away his weapon he rejects the path his father travelled down even if that means death.
Vader and Luke teaming up against Palpatine sounds more like the John Milius version (actually a John Milius style spoof cut would be a gas to watch). It's also rather like the PT duels of two good guys against one bad guy (or three when Mace tries to arrest Palpatine in ROTS).
When Luke throws away his weapon he wins, when Vader throws Palpatine down the shaft he stops losing.
If they both team up against the Emperor it just becomes a Force enhanced pissing contest.
You might as well have Vader retreive Luke's sabre and stab Palpatine in the back with it and declare himself Emperor.
People who objected to my suggestion of restoring the original title should be against a change of this sort (if it is possible to do).