well.. id like to make a correction...
it is safe, however.. its usually not a good idea becsuse YOU WILL NOT be able to install the final version of 10.2 over your beta of 10.2, and it is not a good idea to install 10.2 if you use your computer for important stuff, cause its buggy...
i would be against installing 10.2 over your existing install. i would create a new partition or use an extrernal drive.