The new XCode 4.2 and presumably the next versions of it do not ship with a real GCC, which is one of the things mentioned in the article.
This causes problems for software that doesn't compile right with LLVM yet (arguably bugs in the software, but tell that to someone who can't use the LLVM compiled binaries any more).
Eventually, the version of Xcode that includes GCC will be too old to do anything useful with.
So then you wouldn't be able to "just install XCode", unfortunately.
They will ship with a different compiler, clang, and then with homebrew you can compile and install GCC to your hearts content.
For all of my personal projects and projects at work I am using clang because the errors and warnings it gives me are clearer, pinpoint the problem and it compiles my codebase almost 30% faster than GCC.
This causes problems for software that doesn't compile right with LLVM yet (arguably bugs in the software, but tell that to someone who can't use the LLVM compiled binaries any more).
Eventually, the version of Xcode that includes GCC will be too old to do anything useful with.
So then you wouldn't be able to "just install XCode", unfortunately.