TRIM is the best thing to happen to SSDs since the price of flash memory started falling. Now part of the Serial ATA specification, this command allows solid-state drives to clear flash pages filled with data that has been deleted. Those pages would normally be marked as available but remain occupied with old data. Since overwriting occupied flash pages is slower than dumping bits into empty ones, TRIM can improve long-term write performance quite dramatically.
Solid-state drives have supported TRIM for years, but the command has never worked on drives participating in RAID arrays. However, Intel has now enabled TRIM support for RAID 0 arrays tied to its latest 7-series chipsets. You'll need to be running the RST 11.2 drivers (available from Intel's Download Center) in Windows 7 to pass TRIM commands to solid-state RAID arrays. Intel is also working on a Windows 8 driver with similar TRIM support, including the 7-series chipset limitation. Looks like last-gen platforms are out of luck.
AnandTech has put the new drivers to the test and confirmed that TRIM is indeed functioning as expected. Support is limited to RAID 0 arrays, though; RAID 10 configs aren't so lucky.
While we're happy to see Intel bringing TRIM support to RAID 0 arrays, it's unfortunate that support is limited to its latest platform. The 7- and 6-series chipsets share the same storage controller logic, so there should be no technical barriers to enabling TRIM on the older platform. This isn't the first time Intel has denied TRIM support to an older product, though. Intel released a TRIM-enabled firmware for its second-generation X25-M solid-state drive, but the first generation model, which uses the same flash controller, never got TRIM support.