You've seen the touch-oriented Metro interface with tiles in reorganizable groups, where the faces of the tiles change programmatically and you can pinch to zoom out to view all of the tiles at once ("semantic zoom"). In the Consumer Preview, Microsoft promises we'll be able to create and name new groups, drag groups, change the background color and style, turn big tiles into little tiles, and use the mouse (not just our fingers) for all sorts of navigational actions, including semantic zoom. There are several minor changes in the way you swipe and click, particularly with the charms bar (Search, Share, Start, Devices, Settings) on the right. These changes are largely cosmetic, but if you're thinking about deploying a Metro app -- especially a Metro app that has to live in a mouse-friendly world -- they could be crucial.
Also on the Metro side of the fence, the current, reprehensible App Search behavior changes: Instead of Search splatting an alphabetized list of all your applications on the screen, as the Developer Preview does now, the Consumer Preview arranges them by groups. You'll probably want to work with it a bit, try rearranging and renaming groups, and see if your users can live with the new tools at hand.
On a "legacy" Windows 7-based PC (a loathsome term), more changes are in store. It still appears as if all Windows 7 apps and drivers will just work on Windows 8 PCs -- that is, desktops and laptops using Intel or AMD x86 CPUs. That's certainly the goal, anyway. In the Consumer Preview, we'll see a few changes: an improved Task Manager with more details and app startup tweaking; the new Windows Explorer ribbon won't appear by default as it does in the Developer Preview (yes, Explorer will still have the "up one level" button, as well as the Open Command Prompt menu item); a few long-overdue tweaks to the copy and move dialogs. They're all worth a look, though nothing's really compelling.