A couple of things:
In 5.5 in remembers my last setting for substitution variables. I.e., should the editor prompt me for the value or not. 6.0 doesn’t seem to do that.
That’s mostly an annoyance, but if I come into sql nav (or open a new file to run) and forget to click on the :& I get an error ‘Encountered the symbol “&”…’ BUT, even if I click on the :& I continue to get the error and I have to exit sql nav to reset it.