I don't think this is Apple trying to be difficult: SSD TRIM is buggy between all the different vendors (today even Ubuntu enables it only for Samsung and Intel SSDs by default), they want to guarantee that it works by whitelisting what they ship with, and the mandatory driver signing seems like a security improvement. If some third party wants to ship a signed kernel extension that works with their specific SSD (or generic ones, even) and supports TRIM, that should be possible.<p>FWIW, there is a third party SSD drive that works with Apple's default drivers for TRIM support; I suspect they're doing some sort of identifier spoof to fool the whitelisting code:
<a href="http://www.angelbird.com/en/prod/ssd-wrk-for-mac-929/" rel="nofollow">http://www.angelbird.com/en/prod/ssd-wrk-for-mac-929/</a>