We are using a 3M PAPR that has a fairly small battery. Even with that, when you are required to carry multiple BZ samplers and a radio on your belt under your PPE, in addition to the battery, into an area it is still cumbersome. PAPRs are typically only required in areas with elevated airborne contaminates (or potential for) requiring an increased protection factor. Cost is an issue and use in the cold can be an issue, one person I worked with froze her tear ducts wearing one. They do reduce stress of long time respirator use and help to some extent with heat stress.
Using them for moderate to heavy work does require the user to modify their work routine but unless you can do some decon or implement engineering controls (or talk RadCon or Industrial Hygiene out of it), not much option.