Hi usana,
Welcome aboard; I see that is your first post. People who have never used a porta-potty are often grossed out by the idea of it. Consider being in a boat for more than a couple hours without facilities? :disgust The PP is easy to use - slide the lever open, do your business, slide the lever closed. Put a bit of proper chemical in there, and there is no problem with odor. We have had PPs on our previous boats, problem-free. The head on our 25 is a Dometic/Sealand which, for all practical purposes, is a big porta-potty that has to be pumped out (or dumped with the macerator pump). The only advantage of this head over a typical PP is the capicity (we can go a week or so, being conservative). The disadvantage is that you can't carry the holding tank to a toilet or dump site. I have never known a marine head that didn't plug up... and then you WILL be grossed out.
The lowly porta-potty has a lot going for it: low tech, easy to use, easy to dump, portability... and if you do have a problem (not likely), toss it and get another one for less than $100.
Spending time on a boat means you will have to deal with the potty situation... just because it is a little different from the toilet in your house causes concern for those new to the situation. Fear not - know you can boldy GO where ... well, you get the idea.
Your real concern should be: how soon will I feel inclined to give up a good paying career and become a boat bum? :wink:
Again, welcome aboard.
Jim B.