Money from TP2 sale (who wants a TP2 on the used market over a discounted Evo through a friend's account), possibility of the corporate discount not being applied to the new plan, surcharges/taxes, and the long-term situation with these Evo fees (4g, HotSpot, going up/down??) are all variable and potential deal breakers in my situation.
Have you considered calling up retentions and see what, if anything, they can do for you if you agree to drop the SERO goodness and sign on for two more years? One may argue that you're being asked to pay 3x/mo for basically the same thing you have now, at least for negotiating purposes
They may just laugh at you, but it is becoming increasingly obvious that Sprint is actively trying to convert the SERO subs to more profitable (or profitable, period) plans.
I wonder if the inflated $350AR TP2 price (latest and greatest SERO device) and the bargain-of-a-price $200 Evo price are intentional parts of their strategy to increase ARPU.