Originally Posted by UAalltheway
It depends on upgrade avilability when using miles. If there's open upgrade seats when you try to apply the miles than you will be immediatly confirmed into the seat(s). If there's no current open seats when you try to apply the upgrade, than you will be waitlisted.
If you really want an upgrade using miles on a particular flight, you could forgo the fine Web site and call instead, asking for the lowest priced itinerary for which an upgrade could be confirmed immediately. Then execute the ticket purchase and miles upgrade simultaneously.
To get upgrades, I use most of my miles for upgrades. In the past 5 years, all as a 1P, I only obtained one free ticket (saver RT domestic in F). I only have about 40K RDM at the moment.