We did that trip in 2008. Very worthwhile. It will give you a new perspective on history. The Crusades, for example, were relatively recent and the Roman empire was not that long ago.
We always travel with local companies so our trip was probably much less in a Western "bubble" than you will have with Viking or Uniworld. We had a private guide and driver in the north, then took the overnight train upriver and came back down on one of the many riverboats. That part was group travel, unfortunately, so we had to travel in the usual small herds.
Re vendors, locals, etc. these are desperately poor people trying to scratch out a living. It was difficult before but now with the overthrow of Mubarak scaring away all the tourists it has to be worse. Good on you for going and please remember that these are fellow human beings. Regardless of beggars and vendors, much of your trip cost is spent in-country and they need it!
I would not give safety a thought. Statistically speaking your risk from terrorism is zero. You are probably more likely to sprain an ankle in one of the temples or on the way out of the bar on the boat.
I kind of smile when I see @Senator's posts. With all the shooting in Las Vegas and now in Texas, I'd guess he is planning to flee the USA due to ubiquitous danger. (Assuming he is serious, that is and not being sarcastic.)
