The seven-year service plan only applies to 2012 models - and that's where you'll take the brunt of depreciation (though less so because the seven year plan adds legitimate value to the car). If your main concern is depreciation, look at 2010 models - those cars are the "oldest," probably have "higher" miles than newer cars, and offer prices that are more palatable than cars that have only been delivered within the last year.
Also, correct me if I'm wrong, but all Vipers and Ford GTs came with three pedals - there are no 458s available with sticks. So if you're looking for that visceral, true manual transmission experience, you won't find it with a 458. This is another reason to consider another model. An F430 or an F430 Spider is plenty of Ferrari fun - especially if it's your first - and the price is way lower than a 458, miles are likely higher (which, in turn, means more gremlins have been sorted, more service has been rendered, and she's more broken in), and if you need to flip it in a jiffy, you won't birth your nuts through your billfold during the depreciation hit.
The only contemporary models available with a stick are the F430 and the F430 Spider, the 599, and the California (outside of the US). Older contemporary models (360, 575M, 612, etc.) can also be found with three pedals, and will likely only see a marginal depreciation hit over time (since they've taken most of the hist already).
Vipers and GTs make me think you're a torque junky. So wherever you go to test drive a 458, check to see if they have a 550 or a 575M. Those are some torquey V12 bitches whose performance and design belie their five-figure price tags.