What we do not know yet about the Nexus One for Verizon is what the plans will cost, and, specifically, what upgrade plans would cost. I believe that for T-Mobile, the $179 price is only for new customers; existing customers pay either $279 or $379. They also are not allowing a Nexus One to be used as part of a family plan - it is a standalone plan (that would lose me if Verizon does the same.)
Verizon may be completely different, of course, but we do not know yet.
And, of course, "spring" could mean as late as June 20, if they are on time.