I'm pretty sure it's entirely school dependent. I've gotten pretty lucky with my holds so far... For example, I got placed on hold at GW, got an interview invite a few days later, and got accepted last week. I got placed on CCLCM and got an interview invite the next month. But I know a lot of schools where "hold" is not a very positive thing and not many people get invites after getting placed on hold. It really depends.