If you want SharePoint 2010 Foundation on your SBS 2008 Read Robert’s Blog!!
While the whitepaper has been updated…there’s some key points:
2. After the migration process is complete and you bring up the new SharePoint site it will look almost identical to WSS v3. That’s because SharePoint Foundation 2010 has a visual upgrade feature that you have to select to upgrade the look and feel of the site. I believe that a major reason why people would want to go to all the trouble of installing SharePoint Foundation 2010 on SBS 2008 is so they can benefit from the new interface.
So after you do the upgrade go into the site settings for the site and select the visual upgrade option to change the look and feel of your site to new SharePoint interface
Always do this on a test box first, never on a production one and put down crib notes for yourself.