Well izzyforreal, I can say I DON'T find T-Mobile's contract based plans to be a good deal at all. Depending on the plan, the money spent in higher rates over the life of the contract is well more than the cost difference of the HD2 purchased at $450 versus $199. Especially if you stayed with T-Mobile over 24 months. Even if you switch to a no contract plan later, there's a $35 fee.
For the Even More 500 talk plan, yes you'd save a little getting the HD2 at the subsidized price. With the bigger talk plans you would not do as well in contract.
Outside of contract, T-Mobile's unlimited talk, text and web plan cost $79.99 and includes unlimited calling to any kind of phone and that also includes unlimited txt, web and picture messaging. Also conference calling for up to 6 lines if you host any conference calls. Sprint can only do 3 way conference calls.
You can
get CoPilot direct from the maker for just $29.99, but you'd also want to consider
the $19.99/year premium services for traffic data.