Were I a Chief Officer of a public safety agency, I would not select a NEXT for issuance. Multiband radios can be a headache for personnel on a critical incident and adding in a 'smart' device is too much of a temptation to some personnel to screw around.
Multiband radios act no different than a mono-band radio. The officers don't usually know which band they are on, all they know is they select a channel and are able to communicate with someone.
Every, and I mean -every- officer I know is already carrying smartphones, so no more temptation than anything else.
The benefit to the Next, and radios like the Harris XL line, is that they have the ability to utilize which ever network is available to communicate. In range of your LMR system? Great, it uses the LMR system. Can't hear the control channel? No problem, hop to LTE or WiFi and carry on.
The APX Next is part gimmick and part good idea. Problem is, it requires a lot of Motorola branded (read: Expen$$$$ive) back end to make the apps work. Some agencies already have that, so it's a logical progression of technology. For the rest, it's the gimmick.