I ran 8gb from Crucial in my late 2008 unibody for six months and awoke to the sound of 3 loud beeps telling me the memory had failed. Crucial sells the correct memory but does not warranty it, something I failed to notice before purchasing. I have now purchased the 8gb upgrade through OWC, who does warranty the memory. This upgrade made significant improvement, otherwise I would now be shopping for a new Macbook. Other than the inability to function with 4gb, this computer still runs beautifully. I need a new battery but don't really carry this one around anymore.