Hi Techboy and welcome to cruise-chat;
since you have already read reviews I won't burden you with another, other than to say that I've cruised with Princess for years and never had anything other than wonderful experiences.
But to take your concerns point by point;
embarcation can always bog down: several large groups arrive at the same time: computer break-down: labor problems: but it USUALLY goes very smoothly. The most important thing for you to do is have all your paperwork in order; pre-register on-line if possible; don't try to be the first one on.
Disembarcation problems are usually caused by inadequate customs and immigration personnel, not the cruise lines.
Virus outbreaks always get big play in the media but they are actually very rare.
Staff problems do occur but they are certainly not the norm and they don't last long; word-of-mouth is strong and swift in the cruise community, to which this site testifies.
And while mechanical problems do happen, they too are rare.
Don't let the horror stories put you off; they are usually written by people who have decided ahead of time they are going to have a horrible trip and, well, you've heard the expression "self-fulfilling prophecy"?
I think the truth is that yes, bad experiences happen but they are rare and they are isolated.
You will love the Sapphire Princess (or Diamond Princess) and you will love Alaska!
Just be sure and tell them what you think of the new $50 per person cruise passenger tax.