Basically, yes. The back end component (optimizer and code generator) is now a 64-bit process. It is important to note, however, that the compiler still generates only 31-bit code. We could not really spring a change this dramatic (starting a 64-bit process) in a point release.
It's also important to note that the transition from 5 to 6 is less intense than the transition from 4 to 5.
ahkielstra