Hi Joebire,
I recently installed a 256 Gb Samsung EVO 750 replacing the 500 GB HDD in my late 2009 iMac 21.5", running latest OS and with 12 Mb of RAM.
Had some early issues which have now been sorted (mainly fan speed and migration issues).
I am very happy now that install has settled down from the minor issues mentioned above.
Super fast speed now, well worth the expense to have install and migration done by a local service agent.