I'm planning my V5R4 conversion to 7.1 The 6.1 Memo to users has the
following:

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Device files may experience performance problems.
Application programs that use printer, display, and communications device file (*FILE) objects might run slower after upgrading a system to the IBM i 6.1 release. Enhancements were made in 6.1 to further protect system data at the beginning of the *FILE objects from accidental or intentional tampering. Device files created on 6.1 will not experience a performance degradation. Existing device file objects will be automatically converted the first time the file objects are restored from a save file or save media and will not experience a performance degradation after the files are converted.
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IBM Support line seems to have no idea what the extent of this problem is, how to detect what files (DSPF PRTF CMNF) will cause this, nor do they have a reasonable solution other than to restore the device files.

I have no desire to restore thousands of device files to many different libraries after doing a weekend-long upgrade process. Nor do I relish waiting around to see if anyone squawks about the bad performance of the "new, improved" upgrade -- not a stellar way to convince users that IBM i is the way to go.

Has anyone seen this behavior after an upgrade from V5R4 to either V6R1 or 7.1?
Were you able to fix it somehow?