I was in Section 301 (last section in left field at that level), which was dominated by Red Sox fans, since that was what was being offered after the front office had sold what they could to season ticket holders. I brought a relative from Boston to root for her team.
There is no public address speaker near that section, so you can't hear the announcements. It's a better view of the field than in right field's Section 234, where a good chunk of the right field corner and the scoreboard cannot be seen. In 301 you cannot see a tiny corner of left field.
The Red Sox fans rooted openly for their team and were not rude or obnoxious. The place really started clearing out after the 8th inning 6-run debacle. The Red Sox fans in my section actually started cheering for the Nationals, when they batted in the 9th inning. I think they just wanted to see more game for their money, but it was funny nonetheless.
40,517 in attendance, new Nationals Park record, which was repeatedly flashed on the scoreboard. I could see a huge throng standing in the Red Loft/Porch and along the right field rails. There were a fair number of empty seats in the 213-214. The Red Sox fan had pre-purchased parking in Lot M, but I missed a turn, got stuck in awful bumper-to-bumper traffic most of the way, and we were late. (No free t-shirt for T-Shirt Tuesday!) We were waved into Garage B at no additional cost, so they must have filled Lot M. A garage elevator and the Park's escalator eliminated almost all walking to Section 301.