Only that the straight and level theory for those hours over the Indian Ocean has taken a hit.
1. As I understand it, there was no 'straight and level theory', except in the very early days. Later, they modelled a wide variety of routes at different speeds and altitudes and variations of speed and altitude to find the ones that best matched the satellite data.
2. The big question all along has not really been at what latitude it made the final transmission, but how close to that position it hit the sea. the assumption has been that it spiralled in close to the arc of the final transmission, but it could have travelled tens of miles from there before finally crashing. It may be sitting on the seabed half a mile outside the area that's been searched, and it seems likely based on the debris analysis that it's within a few miles of the area already searched at the north of the search area.
My personal guess is that someone on board set it to fly to the south pole or a convenient waypoint nearby, and we could probably find it by searching a relatively small area around the final arc that coincides with those course settings. I remember someone pointing out early on that a setting of 180 degrees at constant speed closely matched all the ping arcs.
If this is the end, hopefully we'll be able to crowdsource a drone search in a decade or two.