The SATA TRIM command have been implemented in the OpenSolaris source, build 146. This can be used by filesystems to prevent performance degradation over time on SSD:s by giving the garbage collector feedback on which blocks are no longer in use. This is bugid 6866610. It it still not implemented in ZFS but this is the ground stone for making that possible and there is a feature request for that also 6957655.
Looking into the future the similar SCSI UNMAP command would be of great use for thin provisioning, both for thin devices located on a ZFS LUN and for ZFS residing on a thinly provisioned LUN for example in a SAN.
The later is described in this bug report 6913905.
Talks I have given
5 months ago