Downloaded last night...Failed! Thought it was because I was rooted...unrooted...Failed. Backed up, factory reset...TWICE...Failed! Update is FUBAR'd.
So, I looked in the /cache/ folder where the OTA is stored as "Blur_Version.5.9.905.XT875.Verizon.en.US.zip" and found a last_log file in the /cache/recovery/ folder. At the end of the log file there are these statements:
Verifying current system...
file "/system/bin/mount_ext3.sh" doesn't have any of expected sha1 sums; checking cache
failed to stat "/cache/saved.file": no such file or directory
failed to load cache file
script aborted: "assert failed: apply_patch_check("/system/bin/mount_ext3.sh", "1810bb2ccd607e2f6cfbeafa158bb3a89629d60b7","3a8382950bd4a6226349607d099afcbd93653d48")
E:Error in /cache/
Blur_Version.5.9.905.XT875.Verizon.en.US.zip
(Status 7)
Installation aborted.
From this I infer that a checksum is being applied to the mount_ext3.sh file and the installation is aborted if the checksum does not match. Coincidentally, that is the file that has a couple of chmod commands added to it to keep root permanent. I don't know if a factory reset will put that file back to its original state. I also don't know if it would be possible to restore root after doing so. I also don't know what other checks may fail if that one succeeds. However, it seems clear that VZW is, at a minimum, attempting to prevent rooted phones from taking the OTA to ICS by failing the installation on phones that have used the forever root method to maintain root through OTA updates.