Besides the usual ones, I've had to use IDA Pro occasionally for compatibility purposes in my job as a NAS vendor. There are lots of apps that make lots of ass

Besides the usual ones, I've had to use IDA Pro occasionally for compatibility purposes in my job as a NAS vendor. There are lots of apps that make lots of assumptions about how filesystems behave, generally based on the local filesystem and maybe on one popular networked filesystem for the platform (NFS, SMB, AFP). If one of those assumptions is violated, applications can crash or refuse to interact with you. Some just refuse to write to any networked filesystem. Some run only on whitelisted filesystems. Some will hit an error due to an unsupported operation on your filesystem, fall back to some ancient code path using long-since deprecated Carbon APIs that only work properly on 32 bit systems, and so truncate all of your data to 2 GB. Problems like the latter are really helped by being able to do some reverse engineering of the application to figure out why the heck it just writes out the first 2 GB of the file. Because this isn't our bread and butter but only an occasional tool in our toolbox, the licensing on IDA Pro can be rather frustrating. We use it only once every couple of years to debug some kind of compatibility issue like this, and so we usually have to dig around to figure out if we still have valid licenses, deactivate systems that we're no longer using, and so on.