re: Opportunity's heat shield did serve a second purpose...
"... besides keeping the rover from burning up: It also led scientists to find
the first meteorite on Mars, since called Heat Shield Rock."
One could argue that they would have driven straight past Heatshield Rock heading south from Endurance anyway, but yes, the longevity of the say guarenteed that it was identified as a meteorite...Also, I'm sure the engineers have learnt something from inspecting it so closely.
Debris from the Heatshield also deposited some dust on the Hazcams as well - so it wasn't all good
Doug