My wife uses a PND based on (Intellinav) iGuidance software. She is not a geek like many of us at this forum. She is (just) an ordinary GPS user, who has only learned the basic features of the product. She only knows how to input destination address, and how to look up recent or favorite destinations. That is really all she knows, and that is all that she needs to know to be able to use the GPS PND for all her needs. If you set the zoom level to an inappropriate level, she will see that something doesn't look right, but she will keep on driving like that for many many days, till I notice it and change it for her. I've explained to her (more than once) that the (+) and (-) buttons are for changing zoom levels. I don't think she ever used the (+) and (-) buttons, and I know if I ever change the zoom level too low or too high, she will not know how to correct it again. She just has no use for learning anything more than the very basic stuff. And I think the single one feature that would improve usability of iGuidance for people like her, and also for most of the rest of us, would be a new type of auto-zoom. The type of auto-zoom Garmin (and others) have. A smooth and gradual zooming, as opposed to one big jump as it has always been in all version of iGuidance (2009 and earlier).
Which function of iGuidance do I use the most? I think it is zoom-in and zoom-out. Interestingly, I very seldom need to change zoom level in Garmin Mobile PC.