I wish people would stop saying this. Some apps don't work once you root your device (corporate email/calendar, Time Warner Cable stuff). And on many Sprint phones, the ROMs available are mostly unofficial, unsupported ports of the GSM versions. phones I think it is reasonable to want a stock phone on Sprint, I know I do.
For now, I'm on an LG Optimus G, with Nova launcher, Google keyboard, just sideloaded the 4.3 camera+gallery. If only I could get a solid black status bar.
On Sprint it looks like the upcoming Motorola phone will be your best bet. There are also a couple of Sprint-branded handsets made by ZTE which are close to stock Android. Unfortunately none of these have top of the line specs...
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