PIMA mode lets your throttle run the electric just like the present system, the difference is that you can adjust when the assist and charge happen, and how strong they can get.
If you use MIMA carefully, you can improve mileage, and never deplete the battery. What do I mean by carefully, I mean don't waste the electric, use it with finesse, charge the same way, you hypermilers know all about finesse, this is just one more of the key variables that you can now learn to use to best advantage. Be gentle with PIMA, and you can tune it to maintain charge, and assist just the right amount, with just the throttle,very comfortable, or you can rest your thumb or finger on the joystick and do it in manually in MIMA.
It is up to you. Just like it is up to you to drive the Insight for economy or performance . MIMA just gives you more control. If the IMA is only charging at 4 bars, MIMA will let you charge with all bars, or no bars. If the IMA is background charging while you climb a hill, MIMA lets you turn off the charging, if the IMA gives no assist until you are at 40MPG, and then only gives you 5 bars of assist, MIMA will let you get full assist without stepping down at all, or anywhere in between.
It is difficult to explain it if you never tried it, but everyone has the MIMA grin when they do try it.
Users of the system have learned to increase their MPG by 15% or more.