I dont think anyone full tested this so users would have to let us know.
There was a thread here on discussion of 7.3 and there is really only one change we have seen the guests usergroups is now 5 instead of 4 so all you need to do is make one change in the threads7.php file
Of course we support it or would assist you if you have issues. 7.3 as I stated the only change is whats noted there. Someone gave me access to their site and thats all we found. They changed their group numbers. If you make the change their in that file and do a new install you wont have any issues because you arent upgrading a site.
Be sure that the name of the executable is listed in this variable and that there are no spaces in the path to mogrify.There were 1 WARNING message(s). If you are okay with the warnings, you may continue, otherwise GO BACK to change your config-inc.php or click refresh to try again!