I had nearly maxed out my 750GB HD, and was getting tired of waiting for my computer to do mundane things like open Mail. But otherwise I was very happy with my old machine; the screen looked fine, and it ran Yosemite with no problems other than a little sluggishness.
So I decided to upgrade to a larger, faster, HD, and double the RAM from 8 to 16GB. I opted for a 1TB hybrid mainly because the SSDs are still too pricey, and the hybrid came in a handy kit from iFixit.
I first copied my old HD using Carbon Copy Cloner. I tried SuperDuper first, but it stalled on read errors that CCC skipped over and warned me about afterwards. It also copied much faster than SuperDuper did, finishing the job in about 4 hours where SuperDuper was only about 3/4 of the way through after 7 hours.
I verified that I could boot from the copied drive, then my daughter and I took apart the case, swapped out the HD and memory, and put everything back together. At first startup all I got was a black screen and beeps from the computer. Oops--didn't slot the memory in well enough. Another quick disassemble, fix, and reassemble, and everything went great.
This upgrade was definitely worth it--my machine feels effortlessly fast again. I don't know how much credit to give the hybrid drive versus the increase memory, but I'm definitely glad I upgraded.
- Copy your files to the new drive *before* you install it; you save a step, and can know right away if your new HD works properly (rather than waiting hours for the files to copy).
- Carbon Copy Cloner worked better for me than SuperDuper.
- If you want a clean install, download Yosemite and install it on the new drive before you swap drives, then use Migration Assistant to copy your files. I didn't do it this way, but it seemed like a good option.
- Careful with those screws! One stripped head can ruin your whole day. Might be a good idea to order some replacement screws, just in case.