2011 iMac was soooo slow. Like "click an app, go do errands, come back it's open (unless it crashed already)" kind of slow. Also 1 TB hard drive getting fuller and not helping the slowness.
Repair went well. Found out that Apple added some extra screws and casing when I got my Superdrive replaced a few years ago.
Had a scary moment after putting it all back together when it wouldn't boot. However, it was just me not knowing how hard I had to push to get the RAM all the way back in.
Also saw some punk at the Apple Store carved their initials into my interior when I got a repair a few years back!
Wow. Major speed upgrade. Definitely worth the time and effort.
Beware if also consulting the OWC video in addition to this drive. OWC unscrews the airport card; however iFixit guide just has you disconnect the tables. Wouldn't be a big deal except the OWC method requires a different size screwdriver head that I didn't have! So brief moment of panic until I read the iFixit steps again and saw the other way to remove it.
Also added an extra 4GB RAM I got from iFixit. iFixit parts were overall great, except the SATA cable was a bit too short to easily fit the drive on the back wall, had to angle it slightly.