Samsung SSD in older Imac (24" Alu)? Trim support?
I installed a (Samsung) SSD into a late 2008 Aluminum MacBook, which worked fine.

Apple does not automatically support TRIM for drives that aren't their own, but it can be enabled, for instance with this app: http://www.groths.org/trim-enabler/

Worked for me, just needs to be re-enabled after every system software update.

And yes, my MacBook is now a lot faster, so installing an SSD can definitely breathe new life into an old machine.