Just did the SSD upgrade on my late 09 iMac. I replaced the original HDD with a Samsung 830. Process took me about 1 hour from start to finish. It's actually not that hard at all. My boot time went from 45 seconds down to 15 or so. Apps load up quickly and overall responsiveness is a lot better. However, I did a read/write test with BlackMagic and the results left me pretty disappointed. I know the SSD is working and all but these results are slower than Sata I speeds! Specs are: 21.5" iMac, 3.06 GHz, 12GB ram.