There are only a few known documented changes with SSD support in Win8. Many of them are quality of life changes (convenience).
A built in way to initialize TRIM through the graphical defrag tool or the defrag command line tool. Windows 7 does not have any built in tool for this. You would be required to buy a third party tool for such on demand functionality.
Automatic resizing of the pagefile.sys based on commit usage over time. In a system with a large quantity of RAM this will have a impact on reducing disk space consumption of the pagefile.sys on SSDs. This can be done manually in Windows 7, but requires proper testing, baselining, and a small bit of basic math applied to the collected results of the aforementioned baselining work.
Smarter automatic adjustment of background services for SSDs. Windows 7 made the mistake of disabling SuperFetch and Windows 8 corrects this. This fix can be done manually in Windows 7.
The Disk Cleanup utility and command line tool DISM offers more options to free up disk space from unneeded drivers, patches, and general clutter. Allowing the OS to have a smaller disk footprint than Windows 7. They backported some, but not all of these options to Windows 7.
UEFI + Win8.x + SSD will have the fastest boot times and will provide an experience significantly closer to the instant on of mobile devices (smartphones/tablets).
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