Generally speaking I get upgraded 50% of the time and have to ask the other 50%...but even when I ask they are always obliging.

One thing that helps though is that I always put the comment " **** HHONORS GOLD VIP UPGRADE REQUESTED ****" in the comments section of the reservation.
...every little bit helps !

And thanks to the Flyertalk community (particularly the Hilton forum contributors) for all of their expertise & guidance...thanks to your info my family will be at a hilton in august free for a week while #1 son is at zoo-camp !

Cheers,
the anvil