[greghines]

Well, it's not so much which parts of the SSD have been touched, it's more about which pages have currently-in-use blocks stored in them. If you're using half the capacity of the drive, then it's likely you have a considerable number of empty (or at least erasable-without-needing-extra-writes) pages--especially if your drive's controller does some basic defragmentation.

And no, SSDs aren't worthless without TRIM. But if you're likely to use the majority of the storage space on the drive and do a lot of writes besides, it could be the difference between "fast" and "really damn fast." Either way it'll still beat the pants off most rotational disk drives.

I think the takeaway, though, is that if you've spent potentially-obscene amounts of money on an SSD, wouldn't you prefer that your OS take full advantage of its capabilities to consistently deliver top performance?

(And no, that's not a dig at OS X. I'd recommend that Windows XP users upgrade to Win7 if they're considering upgrading to an SSD simply for the TRIM support. It can make that much of a difference depending on the user.)