Though this only works on Unix, so on Windows it uses the current time as a seed. It might get better results using #microsecondClockValue instead of #millisecondClockValue. And I'd think about just taking the microsecond value and sending it #hashMultiply instead of the weird things it's doing now. (bitXor with the identity hash of the UUIDGenerator instance? That depends on the randomness of identity hashes, which may or may not be very good.) It seems likely that Windows has a built-in random number generator, as well, which would probably be better.
While we're at it, the class Random is a Park-Miller generator, which has quite poor randomness by modern standards. Most other Smalltalks have upgraded -- GemStone uses CMWC (pure Smalltalk, very simple and quite fast; I wrote that one), VW I believe uses Lagged Fibonacci, and Squeak has moved to Mersenne Twister last I heard. I've tested all three against statistical tests of randomness -- generated about 650GB of random bytes from each, ran them through the tests (which require that much data to get good statistics).
All three are pretty good, only failing a few tests. The only generator I tested that passed *all* tests was Linux /dev/urandom. Which is also fast. If you're on Linux, and don't need a repeatable random sequence, I'd use /dev/urandom. If you do need to be able to have a repeatable sequence with good randomness properties, I'd use one of the three generators I mentioned above. Of the three, the simplest and fastest is CMWC.
In Polymath random there are several alternate random generators but I do not if there is CMWC
Regards,
-Martin