The HD on my early 2011 Macbook Pro 13" had been slowing down over time, gradually taking longer and longer to do anything, with the spinning wheel becoming very commonplace. I ran DriveGenius on my machine and it kept popping up alerts that basically told me my hard drive was failing... so it was time to upgrade.
Incredibly easy - quick and painless! I ordered the 1 TB Seagate SSD Hybrid to install (along with the accessory kit with screwdriver, bits and enclosure) and everything arrived within 2 days. (The USB SATA enclosure had a broken USB connector, but iFixit sent me a replacement overnight - thank you!)
Connected the drive via USB enclosure, ran Carbon Copy Cloner and let it clone my existing HD overnight, and then followed iFixit's super-simple instructions. Within 5 minutes I was up and running with my new HD... MUCH faster and MUCH smoother!
Get the accessory kit. Get Carbon Copy Cloner. Get yours.