When I cracked mine I called Samsung and arranged for a factory repair. $163 with two week turn around. Insurance would only have you spend 100. I did not have insurance then. I do now.
So when I do a search on insurance costs for Galaxy Nexus, I see quotes such as $125 for 2 years with a $98 deductible from SquareTrade, and $119 for two years with $70 deductible from ProtectCell.
So assuming these are typical insurance costs, then if you have to replace the screen under insurance, it will cost you $223 from SquareTrade and $199 from ProtectCell. And if you don't need to repair your phone in two years, it will cost your $125 from Square Trade and $119 from ProtectCell.
However, without insurance, if you need to replace the screen, it will cost you $163 from Samsung, and if you don't have to repair your phone in two years, it will cost you $0. And I'm willing to bet that in 6 months you'll be able to find the screen replacement on amazon for half that price. I replaced the digitizer on my Thunderbolt for $32 from amazon including shipping.
So, how is it again that insurance is the way to go?