Just to update…. I decided to downgrade from OS X 10.10 Yosemite to OS X 10.9 Mavericks on the Sandisk Ultra II SSD( a non Apple SSD) and install Chameleon SSD Optimizer to modify the all important Apple kext file. The Sandisk sata interface is negotiating at 3 Gigabit which is maximum interface speed supported by the 2009 MacBook Pro. The MacBook now runs significantly faster -not just at bootup, I have not seen a single spinning beach ball. While it is technically possible to install OS X 10.10 Yosemite on a non Apple SSD, kext signing has to be disabled for TRIM to be enabled. However in OS X 10.9 Mavericks the kext file only needs to be modified to enable TRIM. Now should you intentionally or accidentally reset the PRAM/NVRAM in OS X 10.10 Yosemite, your Mac will not boot. It sees that the kext file has been modified and will not load the driver. It is tricky to get the Mac working again if you are not IT savvy. Unless there is a compelling reason, use OS X 10.9 Mavericks and Chameleon/Trim-enable.
P.S I have written this post on the MacBook.
