I ran once in a x-plus. Wasn't too bad, but my runs are also much shorter (typically a mile). They do sell different products to prevent chaffing that you may want to look into
Edit.
On a side note. Introducing diapers to your workout is like introducing anything else. Do it slowly and ease into it. The first day you do it may e go for a 1 or 2 mike run and see how you feel before getting yourself into a huge amount if trouble.