People standing up and blocking other fan's view during the games is one of the biggest complaints at Nats Park so I understand why the team has created the new rules to try to resolve the issue, but the current policy is a complete cluster foxtrot. The ushers hold people up at the top of the sections until an at-bat has ended, causing a jam up of fans, half of which are clueless and the other half annoyed as hell. Me being part of the latter group, I start yelling at the usher to get out of the way. The problem coming when the at-bat ends and the usher then starts checking people's tickets to see where they sit, moving things at a snails pace. Followed by the slowest moving ticket holders setting the pace down the stairs as the long group trails behind and play starts again. So that by the time most people arrive at their rows the next batter has entered the box and play has resumed just in time for everyone to have to get up and block people's views, exactly as this failed policy has been intended to prevent.
The problem is clueless fans, so holding people up only makes things worse. Signs and announcements are the only way to resolve the issue. Allow people to head down whenever they are ready, but let them know that it's best to try to time their entrance into the row until a brief stoppage in play. Just as big of an issue is people in no rush to sit down, shaking hands with friends, setting down their stuff, and dealing with people in their seats. I had to yell at a couple couples the other night to sit down because they were just standing around chatting, oblivious to the fact that we had men on base with two outs.
One final thing that annoys me is that this problem is associated with DC area fans, I've been to plenty of ballparks and seen the same issue in other places, and at Nats Park as often as not it's the out of town fans who are the worst offenders.
Bottom line for ushers, stop stopping me, or at least speed up the concessions workers since 95% of the time they're to blame for me getting back late.