Windows 7 and Intel's RST (Rapid Storage Technology) have supported TRIM for quite a while, but this support has always excluded solid-state drives in RAID configurations. Fortunately for owners of multiple SSDs who want to put all their precious GBs to use that may change soon, as the TRIM feature will reportedly be enabled for RAID 0 setups in an upcoming RST 11.5 driver release.
Currently the only way for TRIM to function on an SSD is to operate in AHCI mode. Last year users were led to believe that the Intel RST 9.6 drivers would add TRIM support in RAID volumes, but Intel later clarified that it was only for SSDs acting as single drives in AHCI mode alongside a separate array attached to the same Intel storage controller -- but not if the SSD was part of a RAID volume.
The benefits of TRIM are obvious because the write performance of an SSD significantly degrades with time or as the drive fills out without a feature to properly handle garbage collection overhead. This means that SSDs in high-performance RAID 0 arrays could eventually see the increased read/write speeds neglected.
Intel RST 11.5 is not expected to arrive until sometime in Q2 2012 with support for Windows 7 and Windows 8 systems. For a more detailed explanation on TRIM, take a look at AnandTech's SSD Anthology article.