Had to restore to stock last night. An update notice came in, and while I was backing up stuff, and renaming my bloatware back to their original names (updates fail otherwise), the phone restarted itself and went into an endless boot loop. I had root via z4root and other than renaming the bloatware packages to apk.bak I had nothing changed and no custom ROM installed.
I followed the directions exactly, but over the course of two hours the firmware upload would fail at various percentages. I got up to 92% once but most failed at 3% or 14%, when the USB connection would mysteriously disconnect and reconnect. Turns out that the USB extender cable was causing the upload to fail.
Some things I noticed:
The first upload takes the longest, up to a minute, but the other four should go extremely quick. Finally, boot into recovery mode and wipe the data and cache.
If you are on the Download Mode screen, you start the firmware upload, then your Tab restarts and goes to an image of a cell phone with a connection to a computer with a joining dotted line with a yellow ! sign on it, it is still in download mode. Continue the flash attempt according to the original post.
If you try to enter Recovery or Download Mode and you get the above mentioned screen image, continue flash attempt according to the original post. I believe it means there is no firmware to detect the volume buttons and show the correct mode, but this is just speculation.
The long boot up time after the successful flash is normal.
Hanging on the Verizon boot screen for more than 10 minutes is NOT NORMAL. Hold your hand on the Tab. If you feel it vibrate once (beginning of boot) and then double or triple vibrate a few seconds later (boot error), and it continuously repeats this pattern, power off, boot into Recovery, wipe data and cache partitions, then restart. If it still boot loops, retry the flash procedure in the original post.
/worship OP and whoever he stole the walkthrough from for the info. ;p
Connect the Samsung USB adapter directly to the computer, no extenders, no hubs. I also later found out that stalls during the first upload at 41% 62% and 93% are normal.