<font face="Verdana, Arial, Helvetica, sans-serif" size="2">If upon checkin and they have room in business class, what are the chances of having my one economy seat moved into business class - would the fact I used the biz class points carry any weight.</font>
Don't know about the United factor, but if you did that on an AC ticket with AC points, you supposedly have top priority over everyone trying to upgrade. But remember when you're talking to the agent, you're not "upgrading" since you've paid for a Business Class seat (and using the word "upgrade" may affect their response).
andrew