Having the latest and greatest new helps a bit. However, within two years g++ will probably support many more C++0x features than it does now, but since RHEL7 probably won't be rolled out until 2015, you can't use them for a window of three years when the rest of the world has moved on. I am emphasizing on C++ here, because that's what I use mostly, but I am sure that the same applies to Python or Ruby. I like turnaround times of two year max ;).
Before someone points out that Windows has even longer release cycles: that's true, but the Windows 'userland' isn't tied as much to the base system as a Linux distribution. Try to replace Gtk+ in CentOS 5 to a newer version, it is a pointless exercise. On Windows you can install the latest installment of Visual Studio and enjoy new features.