Don't forget with the current zoomer promos, the current zoomer plan works out to about $25/mo for 4gb (until Feb 18?). $36/mo, $100 activation credit, $50 referral credit, plus a phone you can sell for $100+. Only catch is the 24-month contract, but given the freebies making the plan effectively $25/mo, it's not that bad of a catch.
These migration plans are great too, especially if you need BYOD, and there's no other tempting limited time offer (like the current zoomer).
Reason: No referrals