My 2010 MacBook Pro has been slower than a snail to the point of almost unusable ever since I upgraded to mavericks and beyond. Replacing the hard drive for this new SSD has brought performance back to equivalent to a new device. Its faster to boot up than my new MacBook Air I purchased last year, and opens apps faster incredibly fast. Unbelievable that following such a simple upgrade with this HD that I now have a super fast MacBook Pro again. Did not need to buy the new MacBook Air.