As I posted to your same question in another area;
Alaska is one of those places many people only get to do once in their lives, so it's important to do your homework before deciding for or against any one particular cruise line.
Plus, if you look at rates for next year, there are several wonderful cruise ships that are not only nicer than the Carnival Miracle, but on several occasions are cheaper! These include Celebrity, Holland America, NCL, and Royal Caribbean.
Best thing to do is talk to your agent, preferably a Cruise Specialist who's been to Alaska and can give you alot of first-hand information to consider when selecting which cruise is the best one for you.