One thing you'll notice is there are only two files to contend with on the boot disk. As usual, STARTER gets things fired up. It has the job of booting up the other file, the SYSTEM file.
Contained within the SYSTEM file is the kernal, the Toolbox, the Dashboard, and the default input and printer drivers. No other files are needed to get up and running. The very first bootup will guide you through configuring the SYSTEM file and any changes made can be changed again from the Dashboard. All Toolbox functions are accessible from the Dashboard menus. The Toolbox interface will no longer be used.

There is only one Wheels SC version. It doesn't matter if you boot up from a 64 or a 128, it will work with either. If booted up from a 64, it will act more like Wheels 64 and use 40 column mode. If booted from 128 mode, it will act like Wheels 128 and will offer both 40 and 80 column modes.
Wheels SC does not fit on a 1541 disk. It will be supplied on a 1571, 1581, or FD Native disk.

Once booted, the Toolbox and Dashboard will remain in memory. Exiting an application is immediate since the Dashboard doesn't need to be reloaded from disk.

The biggest thing the user will notice is an improved Dashboard. Too early to discuss it too much, but it will have features that let you configure your drives easier. You'll even be able to create partitions on the CMD devices like you can with HD-TOOLS, etc.
Now, when you double click on a drive icon, if it's a partitionable device a window doesn't pop open showing the current files in the current partition. Instead it opens a window showing an icon for each partition. You can then double click on a partition to open it into another window. Anyway, in the partition window, you can rename partitions, create new ones, etc.

The Dashboard will be able to copy files to/from MS-DOS disks. It will be able to access CD-ROM drives connected to the HD.Lots of neat new features will be in the Dashboard.

Classic GEOS and Wheels applications will still work. You'll be able to task switch between multiple applications. The number of apps you can have loaded at one time will depend on available memory. New applications that are written specifically for Wheels SC will be able to take advantage of its multitasking ability. 
New apps can also open up using the entire screen for itself like current applications do or it can run within a windowon the Dashboard. This depends on how the programmer wishes to do it.

Wheels SC will also have all the Wave networking routines built into the OS instead of in Wave SC (also supplied with Wheels SC). This way, other applications can make use of the same routines. This will make it easier to build separate Internet applications that need to do some of the same type of stuff.

The windowing routines from both the Dashboard and The Wave are in the OS. New apps can make use of these routines. This includes routines to make windows that are moveable, resizable, with scrollbars,
function buttons, etc.

Up to 8 drives (A-H) can now be used. 1541 and 1571 partitions are also supported on the FD, HD, and RL. Also, the new extended native partitions on the HD are supported. Current apps may not work well with drives E-H. They probably won't even know they are there. So, the usual drive swapping routines are still employed. Remember, some of the old apps only work with A and B.

I plan to take geoBasic and modify it for use in Wheels SC. This will make an easy to use programming tool for people who can work with Basic. geoBasic is also nice because it can help you build dialog boxes, menus, and other things. And of course, the geoBasic bugs will get fixed. Concept+ will get upgraded to Concept SC and will add more features for those who prefer to use assembly language.

From a programmer's point of view, the operating system no longer resides in bank 0 of the SuperCPU memory. What's in bank 0 where classic apps run is a series of jump tables and a few other assorted routines to make the new system work with old apps. All kernal routine calls are transferred to the actual SC kernal. For new apps, the same kind of GEOS thinking is employed where a jump table can always be found in a fixed location. It is always in bank 2. A simple JSL can call any kernal routine. Selected Toolbox and Dashboard routines can also be accessed from the new jump table. New apps will always be loaded into a 64K bank somewhere in memory. The app will have the entire bank of memory to itself (and more if needed). New apps are expected to run in native 65816 mode while current apps default to 6502 emulation mode.
The kernal takes care of handling the processor mode switching during task switching and multitask handling. The kernal always runs in native 65816 mode.

-Maurice