Hi,
No, it's not really random. From the manual
Random VAR

Perform one iteration of pseudo-randomization on Var.
What you can do (don't know if it's enough though) is to seed to "randomizer". You do this by presetting VAR (stardelay in your case) with a number which will be used as the seed. If you initialise startdelay variable to a different value on each device they won't act the same. Each individual device will, however, act the same every time it starts up - just not equal to the one next to it.

Like I said, don't know if that's "random" enough for you.

/Henrik.