I have a Corsair 128 SSD from the time I bought the MBP. It was a nightmare to make it to work with sleeping. It had a known bug that was corrected after almost a year by Corsair with a firmware update. After this it has worked flawlessly. The machine has 8GB RAM and it is still very fast. It is the last model that came with an internal DVDRW drive, something that I still appreciate and still use sometimes. The hard disk is now very small to hold OSX, programs and pictures. I am constantly deleting things so the time to upgrade has come. I want a >500GB SSD drive to replace it, and I want it to be fast. I appreciate your recommendations as I want to be sure that whatever I end up buying is not going to produce me headaches like the Corsair drive I bought in 2011. At the same time I want something fast and do not want to buy directly at Apple. last time I checked prices for their SSD upgrades they were horrendous! Thanks!