I've used extended batteries for my android phones years, like most users, because of very heavy usage. I am been on Wifi all the time! Got my Note 3 a month ago and I am still getting used to its huge screen lol... This is the first I’ve even heard of MPJ, mostly are positive so I give it a go. Fired the new battery up for a full days and think it definitely worth of use. Here is what I experienced with it, but only sharing my day to day usage, not an in-depth review.
There were a few times that I turned on gps (nearly one hour) while out and I usually surfing webs or streaming music (35% volume) for hours while commuting. I put bluetooth/4G/auto-brightness off. Went back home around 6 p.m and the battery remained 60%. I want to know its limit so even went out of my way to kill it by playing games etc. Next day I played heavy->moderate data and it finally die that night.