Suedrews,
I'm not a spokes persons for Sprint PCS, in fact we had some problems with our past bills, but they eventually cleared them up.
My wife and I are on the family plan (2 phones) with PCS to PCS and when I travel I can call her from anywhere in the US to her anywhere in the US, cell phone to cell phone, no minute charge (meaning you do not get charged for the minutes used and no long distance charges). I can also call my friends and associates who are also on PCS to PCS plan and not get charged for the minutes. In fact I'm looking at our bill and a 160 minutes were exchanged between us for the month. Also, if you are a member of USAA (Military Banking/Credit Union) you can get 5% off the service fee. There is no rollover benefits, but with PCS to PCS and free nights and weekends, we never use up our 500 primetime minutes. And if it helps, for our two phones here in Chicago, the Additional Charges ( the stuff you don't see until you get your bill: Taxes, Regulatory Related Chages, 911 Surchage, etc.) comes out to about $16/month ($11 for the 1st phone, $5 for the 2nd).
Haven't used the phones at WDW yet, but they worked great at DL. Hope this information helps.