Yes, TRIM works on software raid in W7.

I've got the results back home. (I'll get to them late next week)

Like overthere explained, one can monitor the time it takes for the drive to "perform" the TRIM command.
If you recall one of my earlier runs comparing VMs, the SF drive came out pretty bad* because of the time it took to TRIM the drive.
(* it could have performed very close to the C300 if it wasn't for the TRIM "bug")