After 3.5 months with the MIMA modification, and about 4000 miles, I believe it's now safe to conclude that the MIMA mod. has enabled a 15% improvement in fuel efficiency, compared to the same season in previous years without this mod.
Excluding increased tire pressure, the other "passive", (but no less elegant) modifications have been temporarily disabled for the summer season, so this controlled experiment can for the most part, isolate the MIMA influence.
With regard to the emotional factor, the novelty still hasn't worn off. MIMA (and to a lesser extent PIMA) are interactive, and therefore downright engaging.
While it's not all that difficult with cooperative climate, terrain, and careful driving technique to achieve > 100 mpg in a stock Insight; in less than ideal conditions for high fuel economy, the MIMA modification isn't a panacea, and it doesn't change the laws of physics. Climate, weather, terrain, and driving technique remain major factors in ultimate fuel efficiency.
Traveling East/West through north central Massachusetts, the hills are very long and relentless, and the Insight battery pack capacity (with or without the MIMA modification) doesn't coordinate well with the terrain. Despite all my best efforts, it seems nearly impossible to exceed 80 mpg on most of that route, and I only exceed 80 mpg by "recovering" in the relatively short segment in the east where the hills aren't so long.
On a recent trip to Cape Cod, the FE was 100 mpg over the 150 mile distance, 90+ % highway, with the windows open. There were big hills over at least 70% of the route, but many of the hills weren't quite so long, and there were some segments where the battery pack SoC could be restored.
I don't believe there's any way to get even close to 100 mpg in an Insight on that very hilly route without the MIMA modification, traveling at legal speeds, and not drafting trucks or RV's in very close proximity.