Yes, I have done millions of them, or at least it seemed that way.
The whole process, from start to finish takes about 2 hours, depending on the size fo the database. I say 2 hours, because the book has you print out the DNB, TNB...yada..yada...and that can take a while. The actual upgrade, 1 hour, 1 hour 10 minutes tops, unless something goes horribly wrong. I have done about 25 upgrades and have only had 1 Option 11C go bad, and one 61C go bad and both were caused by things not in my control, or the control of the on-site.
make sure your pcmcia card has all the software on it. Make sure you have a win95 laptop with a pcmcia slot available. if you get a bad pcmcia card, you will need the win95 to quickly copy the software off the net. This will work, I have had to do it.
It's real quick though and pretty painless.
1. prints
2. rom upgrade
3. archive
4. upgrade
5. patches
6. schedule firmware upgrades, if necessary, but you don't have to stick around for this.
7. test calls
8. go have beer
not necessarily all in order, but those are the quick steps. Follow the book, it's pretty close.
hope this helps.
John