By instant upgrade, are you talking about a status match? If you do the (currently free) challenge (and you can do their challenge every two years - unlike status matches that are usually once in a lifetime), you start as Silver and move up depending on your US-metal miles during the challenge. You might miss a few upgrades along the way since you don't start at the top level, but I wouldn't be surprised if you average 50-90% as you work through the 30k miles it takes to get CP on the challenge.

There are some annual surveys on the US Airways forum, and results vary tremendously, but in general Silver averaged around 50%, Gold 60%, Platinum 70%, and CP 90-100%. My own experience was 78% as Silver and 100% as Platinum. (I just hit CP and won't have my next flight for a few weeks.)