Andy,
I'm trying to ensure that all my sites are moved correctly prior to updating DNS. In the cases of all other PHP sites, I have seen no problems as long as I remember to set the base URL to http://72.9.232.146/~<userid> temporarily (I will switch it back once I update DNS). In this particular case, the PHP is not critical to the site operation so, assuming you reckon I won't have a problem (a PHP error displayed on each page is not acceptable!), I'll go ahead and update DNS then keep my fingers crossed that everything works OK once the change has rippled through.
Thanks,
Dave