As the announcers and press couldn't stop saying, this is the first time a Washington baseball team has been in the playoffs since 1933. This is true; the original Senators last saw post-season play in that year, winning the American League pennant with a 99-53 record before falling to the Giants in the World Series. After that, 27 years in the second division followed with second-place finishes only in 1943 and 1945.
After that they moved to Minnesota, which is another story.
The expansion Senators were every bit as bad as the team hey replaced, with exactly one winning record (86-76, in 1969) before moving to Texas in 1972.
Even the history of the Expos is nearly devoid of playoffs, the only exception being the strike-shortened 1981 season, when they beat the Phillies to take the NL East championship and lost the pennant to the Dodgers. Since the move down here, of course, the team took a while to recover from being mismanaged by MLB and Jim Bowden, respectively; this season is the first time the Nationals will have had a winning record since moving here from Montreal, the previous high point being the first year (2005) when they managed an 81-81 record and still finished last in the NL East.
So people are pretty excited about this. As I said previously on Facebook, having seen the Twins' playoff teams from 2002-2006, I think the Nationals have a chance to go all the way to the Series. The pitching is phenomenal, there's power all over the infield and outfield, the defense is good, and there's a decent amount of speed, though that tends to be overrated. We'll see how it all works out. I am very much looking forward to this.