Hi Converse, I had the exact same effect when I switched - only took a few minutes because it was effectively a new full tank of 98 - noticeably less pinging. Then I put in new plugs, put the timing back a bit more, then added a new fuel filter a couple tanks later - lots of sludgy muck in the filter when I cut it open. Much better now, but I still need to put it back slightly.
Knock sensors have probably prevented a huge amount of engine damage over the last decades they have been used - most people wouldn't even give the noise a second thought now.
My mates sister blew the engine in her car a couple years ago - ran it out of oil.
Her father said she surely must have heard the knocking/flicking/ticking noise that an engine running low on oil makes, she said that the noise was annoying her so much she put on the radio full bore.
Apparently he went off big time and by the time he had to stop because he was turning purple, she was in tears.
