Windows (7) will usually automatically turn off Defrag when the SSD drive is detected by running WEI.
I think it is actually the Win7 installer when it detects a zero rotation disk. Sometimes SSDs show only a WEI with a 5.x value - e.g. when they are not well aligned. I wonder how running the WEI would handle that.
I'm too lazy to look for it right now but I thought I read somewhere on OCZ forums that said running WEI "automatically" enables/disable certain things for their drives. I could be wrong.
Let's not forget that WEI is also used to detect hardware, so in a sense using WEI will enable/disable certain functions of hardware since it has detected the type of hardware in use - in this case an SSD drive.
The backbone for the Windows Experience Index scores comes from the same new technology built into Windows Vista that enables it to scale, called Windows System Assessment Tools (WinSAT). These tools run tests that discover and assess the performance characteristics and capabilities of a PC. Based on this data, Windows Vista "scales" itself, thereby optimizing the user experience and feature level it delivers for a given computer. The WinSAT data is also available via the Win32 API in order to enable software vendors and internal developers to take advantage of WinSAT data in order to develop software which determines the optimal application settings based on that system's performance capabilities and scale itself.
Windows Experience Index: Overview - though this is talking about Vista, 7 basically works the same way. Anyway that's the way I see it but....
At any rate I found this, which also says defrag should be off -
SSD Tips and Tweaks | OCZ Technology