When upgrading from a spinning hard disk to a solid-state disk in your Mac, you may experience slower startup times than expected. Solid-state drives should be booting your system in 15 seconds or less--a considerable upgrade from traditional hard disks--but failing to set your newly installed drive as the default startup disk can keep your boot times slow.
Apple Discussions commenter "Luis Ortega" writes:
I just installed a 256gb ssd drive (from OWC) into my 2007 Santa Rosa 2.4 core 2 duo 17" macbook pro.
I had done a clone from my old hard drive (7200rpm 320gb) while it was still in the mbp to the ssd drive in an external enclosure using Superduper.
It all worked correctly and then I replaced the mbp hard drive with the new ssd drive already installed with my cloned system and the computer worked normally, except for a very slow start time.
From the moment of pressing the on button to the screen with the apple is 35-40 seconds every time. It goes from off to the gray screen almost immediately but it stays there a long time before changing to the screen with the apple.
This is significantly longer than it was before.
Though the suggestions to reset the PRAM, check and repair permissions, and check the hardware of the new drive are all good, the solution may be even easier.
Mac OS X Hints commenter "noworryz" offers this answer:
The fix is to go into System Preferences >> Startup Disk and select your new solid-state drive. This prevents a 30-second timeout before the boot starts.
Have you replaced a spinning hard disk with an SSD? What was your experience like? Let me know in the comments!