At this point, the only upgrade we know of is that it is going to be 3D and digital and likely at a higher frame rate. But the screens seem to be significantly larger than Soarin' so it will feel more immersive.
The loading is separate from different levels which will likely allow for much greater movement, so I think we'll see a lot of falls and sideways movement (significant movement, not the little tilting that you get with Soarin'). Plus there's the possibility that they've have some randomization for different experiences on multiple rides.
When I heard that the loading areas were on three levels, I got the impression that this was for speed of loading, rather than movement of the cars. For example, in Soarin', after picking up guests, the ride vehicles are stacked horizontally, but then return to the floor.
By loading horizontally, the loading procedure will be noticeably faster as you don't have to walk around a big loading area. I don't know about you, but I've almost gotten lost trying to follow the CM into Soarin's loading area (in DCA), as they just don't seem to have the manpower to load large numbers efficiently.
With three levels it will be short and sweet, like Star Tours a doors will open up and you probably walk down a row without wasting money on CMs, and/or time, guiding everybody in. Plus, it might make it easier for the CM to check the safety belts.
Soarin' has a big screen already, plus if you can't see the pixels, how will it help having a bigger screen, further away, in higher resolution? (Not really sure if Soarin' uses digital projectors, might not). Unless you are talking about having the screen bend more around the peripheral vision areas of black nothingness you have on the ride.
Not so sure that the screens will be bigger, also.