Being that I have no problems with my memory cards I must agree with this statement. I DIDN'T make a backup, I set aside about an hour to do the upgrade, wrote down all my must-have apps and then did the upgrade. I installed python first and then everything else. I have had minimal (read as no) problems and the touch screen sensitivity is back to highly acceptable standards. An interesting side effect of this is that I even attempted handwriting recognition and it 'almost' works now as compared to useless before.
I use my N800 in pretty critical situations and have had yet to experience any breakdown.
Do it!