Dear Aunt TUAW,
Every time I install a new Xcode beta these days, it kills my production Xcode and I can't submit to App Store. What gives? I thought you said that Xcode installs could live side-by-side in separate folders!
Your loving nephew,
Although you can use separate folders for each installation of Apple's IDE, many of the tools used to create and submit packages live in the /usr/bin directory. And, when it comes to a shared folder like /usr/bin, the rule is last-installed-wins -- your subsequent Xcode installation will overwrite the older versions of the tools in that folder.
To get around this you can disable the UNIX Development install option on the "Installation Type" screen of the Xcode installer. This option, which is enabled by default, adds command-line development tools onto the shared install volume. Unselect it during your beta install, and you should be able to skip the development tools re-install when you use the older Xcode version.
Auntie adds that qualifying 'should' because a good fresh install of a release Xcode almost always fixes any problems left around by a beta install, even if you pick all the right options while installing.
Hugs and good luck,