I have had every iPad from 1-3, and now the Mini.
iPad 1-2 were stellar devices, but the 3 no matter how clear the display is was a MINOR misstep in my opinion. iPad 3 has a gorgeous display but had about the same performance of the iPad 2. The weight though not immediately obvious became very obvious the moment you picked up an iPad 2. It's not to say the iPad 3 was a bad product, but having had so many of these at this point it felt like a bit of a let down.
I am not your typical user.
iPad Mini was very much a great step, and probably the best iPad in terms of "Wow" experience since the original.
The size, performance, fit and finish are remarkable.
The use of a retina display would put this well over the top in this category.
Downfalls of iPad Mini? Keyboard usage when trying to use it like a laptop is less then what it is on the full sized. That's really about it though. The weight and size are dramatically different enough that even after a week of usage, closing it with my Smart Cover and seeing its diminutive size feels like something isn't right.
I will absolutely be picking up another 10 inch once they get it a bit lighter. Right now though, the iPad Mini in my opinion is the definitive iPad.
Things I'd like to see in the next full sized iPad? In the same way the iPad Mini benefits from the original iPad display getting thinner, lighter and more power efficient I'd like to see the same happen for the retina. Obviously it's only a matter of time. I think a full sized iPad that weighs maybe 20-30% more in the same slate finish with chamfered edges would be a slam dunk.