Sprint-Nextel's
iDEN network has improved to an all-time best now, so work has been done for
iDEN customers - including the expansion of a handset portfolio that has come to a halt in previous years. But, go with
iDEN only if you definitely use the PTT button for instant communication with coworkers or friends/family; otherwise, check out Sprint's many new
CDMA handsets and rate plans that enable affordable data. If you do seek the button, and want the best of both worlds, they do offer what they called HPTT or QChat, and offer a Sanyo and possibly couple of other options that allow PTT on
CDMA (check compatibility & markets with a Sprint rep before buying).
And, if you want a smartphone with Direct Connect (PTT), then they offer the only new Blackberry in the market - BB8350i, which includes WiFi for data.
We cover more info like this on our blog, but I cannot post links yet. You can find our SmartphoneHeaven blog on Blogspot, or get info and links at Twitter/pdacart.
Good luck with your choice, and hope this helps.