I upgraded from Linux Xampp 1.7.3a to Xampp 1.7.7 today and ran through all the included apps and security script. Everything worked as expected. I modified all the configuration files that my environment requires, and restored and upgraded my mysql databases. I then installed my website into htdocs and tested it out. I am really surprised how smooth the overall upgrade went.
However, keep in mind I have been going through the same procedure during the later stages of the beta program so I have already worked out the most difficult problems most all of which were associated with the mysql database changes.
Note, I did not use the "upgrade" version of Xampp, I installed the full version and then modified it file by file.
Hopefully your upgrade will go smoothly as well.