SSD TRIM Support in RAID 0 or Concatenation

Did you order the 2xSSD config from Apple? If so, then yes, TRIM is enabled on the devices no matter what configuration you put them in.

Remember RAID 0 if one drive fails you lose all your data.

RAID0 performance is worth the additional risk, IMHO.

Just make sure your backup system is robust.

I use Time Machine + Crashplan.

Despite other responses, I believe that at the moment, the only way to pass trim in a raid volume is to set it up using Softraid.

Not correct.

Software RAID in it's current iteration cannot pass hardware information about it's component parts to reporting utilities.

If you 'get info' (disk utility, system info) about the hardware pieces, they will correctly report attributes like SMART and TRIM.

I should clarify...
Softraid is paid software, though you can do builds with the free trial.

Here is an excerpt from their site.

SoftRAID version 4.5 includes all of the incredible features first seen in the version 4.0 release that shipped a year ago. Most of these features are not found in any other RAID solution for Mac OS X. These include: Fast Mirror Rebuilds which allow a mirror (RAID 1) volume to be rebuilt in minutes rather than hours, full validation of all data on volumes and disks, certification of disks to ensure that all sectors can read and write data correctly, a complete email notification system to remotely notify you of any disk or volume error, use of SMART data to predict disk failure and a command line interface for all disk and volume functions. It is also the only RAID solution for Mac OS X which supports TRIM on SSDs.

It's oft misunderstood...

Using software/hardware RAID results in a 'volume' that is composed of multiple 'physical' devices.

TRIM (and Garbage Collection) is a firmware/hardware function. It could care less about the volume structure it's a part of.

By default, Apple enables TRIM on any Apple-branded SSD. There are multiple ways to enable TRIM on non-Apple SSD's.

The performance of a particular SSD is dependent on the OS being TRIM aware, the firmware TRIM and the Garbage Collection routine. All 3 are necessary for optimal performance of a SSD.