My personal experience is that gold frequent flyer status counts for nothing when it comes to upgrades. Indeed, it seems to be gold status is a disadvantage.
I am Gold with both BA and Star Alliance (Diamond Club). I have flown business class long haul return at least twice a month with either BA, BMI or Lufthansa since January and not been fortunate to be upgraded once. However, colleagues travelling on the same flights as me, and having paid the same fare, but with only Blue or Silver status were upgraded to FIRST with BA on at least 4 different ocassions already this year.
My frequent flyer status is in the system before I reach the airport and I've even been standing in the check in queue with them, so it is not to do with timing either.
Indeed, I have even been downgraded to economy on one flight with *A (flight overbooked - not happy) and a colleague I was travelling with who had blue status only was kept in business class ahead of me.
It seems more likely that if you are gold, they know you are a regular traveller with them and need to do less to keep you, whereas if you are blue or silver, then perhaps they can do more to entice you to choose them over competitors.
I have no complaints over not being upgraded - business class is more than comfortable. I do have complaints over being downgraded, but the carrier seems unprepared to do much about it other than refund the difference. I won't be flying with them again.