Until late last year, I never had much trouble with PTT over iDEN depending on what building I was in, always worked fine outside. No carrier guarantees coverage inside a building plus these are old buildings that are built like bunkers and no network works. We have iDEN repeaters to solve this issue that we'll be switching to CDMA. Also, not all phones are equal.
One thing I will miss about having an iDEN phone, had a tornado warning about a year ago (no touchdown/damage) shortly after Joplin, MO was hit not far from me, the non-iDEN phones couldn't get through.