A Porta-Potty is a nice convenience when camping for those late night trips, and you don't want to go out scaring up any wildlife. A lot of pop ups have a cabinet that will store a porta-potty. Odor really isn't an issue if you use tabs or some deodorizer. However there are also shower tents that some put their porta-potty in to keep it outside of the pop up.
In our pop up the cabinet to the right of the door as you enter is the porta-potty cabinet. In our years we've been through three different pottys, the first one popped a hole in the bottom from being slid across the floor. The second one never made it to the second trip, it leaked out of the box. Then we bought a Tetford, and have had that one for about ten years. One mod I did was create a short base for the potty. Not only does it give the seat a better height (for the ladies) but the added wheels allow it to roll in and out of the cabinet easily. They are one direction wheels by the way, don't want anyone rolling out the door while going potty!
Update 2020: I made the slider base as wide as the porta potty which meant you had to have perfect aim to slide it back into the cabinet. I took about an inch and a half off the width and tacked on a piece of sticky cloth on top. Now the potty slides back in much easier and doesn't slip on the slider.