Sprint is trying to remove TPs from circulation due to the high occurrence of malfunctioning. They will not give you any phone you want, but rather have a list of phones they can offer you. There is more info here:
http://www.howardforums.com/showthread.php?t=1577243
In addition there is a couple threads open on this site as well regarding the issue. Both are titled something like "Sprint replacing TP with TP2!"
Anyhow, enjoy your new phone. My wife's replacement is supposed ot be in tomorrow as well.