OP - I'm with you on the hating IAD issue.

I'm 6/10 on E+ upgrades on United, with US silver. On 2 of the denials, it was because the flight was overbooked and there simply weren't ANY other seats, and the other 2 were GAs with attitudes. I also found that overseas codeshare agents (LH in particular), were very willing to put me in E+. I generally try to ask really nicely and not act like I'm entitled to the upgrade.