If it worked on every network/provider with ease..
Otherwise what's the point? If you buy it out right and go month to month and at some point for whatever reason want to switch providers, but the phone won't work with the new provider (cdma vs gsm, fixed radio frequency, etc). Now you have to take a loss from reselling the phone or deal with your current provider.
Moe, I need your advice
See I've got this friend named Joey Joe-Joe... Junior... Shabadoo..