I have used exFAT extensively in both OS X and Windows on the same computer, switching between the two operating systems. It was nice to have a read/write drive available to both operating systems without running any third party software. Unfortunately, initial OS support for exFAT was pretty bad on both sides, maybe beta quality at best. I had corruption issues about once every two or three weeks.
When this happened, Windows would switch to read-only mode for the exFAT drive, I assume out of fear for making things worse. OS X just merrily kept using the drive, resulting in all manner of weird problems. In OS X, Disk Utility refused to repair exFAT drives, although I could drop to the command line and fix it there. Windows CHKDSK could usually, but not always, repair the drive. I never lost a file though.
Also, none of the backup programs I used would work with the exFAT drive in any capacity. They won't back it up, nor will they accept it as a destination for backups.
However, today it is a completely different story. Same drive, same computer, but newer versions of OS X and Windows. It works very reliably now, no problems. (Backup might still not work...I haven't tried that in years.)