We are having issues with some of the modules when working along core modules.
1- search would not work when FCKEditor is activated
1a- when performing search the page goes blank
1b- several database errors show up when cron runs in the admin section
1c- teaser split doesn't work
1d- text body field doesn't show up when fckeditor is activated
the only difference between FCK and Nicedit is that the search results works with nicedit but more problem come up with working the text body field.
4- pathauto doesn't update when performing a new bulk change. you basically get one chance to set the records
4a- pathauto gives a lot of database errors
4b- pathauto and taxonomy and custom content types can't seems work together properly
