Most of the corrupted files are completely unreadable. The JPEGs typically decode partially, up to the point of failure. So if you're lucky, you may get most of the image except the bottom part. The raw .CR2 files usually turn out to be totally unreadable: either completely black or having a large color overlay on significant portions of the photo. Most of these shots are not so important, but a handful of them are. One of the CR2 files in particular, is a very good picture of my son when he was a baby. I printed and framed that photo, so I am glad that I did not lose the original.
If you're keeping all your files and backups on HFS+ volumes, you're doing it wrong.
HFS+ is a weird vestigial pre-OS X leftover that, for some reason, Apple just does not replace. Apple tends to be relentless when it comes to moving on from past code, but HFS+ just refuses to die. As John Siracusa, long-time critic of HFS+, stated way back in 2011:
I would have certainly welcomed ZFS with open arms, but I was equally confident that Apple could create its own file system suited to its particular needs. That confidence remains, but the ZFS distraction may have added years to the timetable.
Three years later, and still nothing, and with Yosemite also shipping with HFS+, it'll take another 1-2 years before we possibly see a new, modern, non-crappy filesystem for OS X. Decades from now, books will be written about this saga.