I'm using Tom Tango's calculations for WAR, Bill James's projections for hitting, and CHONE for pitchers. Why these projections? Because I like them (and they're free and handy). The playing time projections are my own. For fielding, I used each player's UZR runs above average for the last three seasons, regressed to the mean.
A replacement level team would win about 47 games, so by adding the individual WAR of each player, I project the current team would win about 74 games.
For comparison, the Nationals were a 66-win team last season based on run-differential, so my projection says they're about eight wins better than that. You shouldn't compare the 74 wins to the team's actual win total of 59, since WAR projects wins based on pure run differential--the bad luck, lack of clutchness, bad managing, or whatever it was that accounted for the seven game gap in the Nationals' 2009 actual win total and Pythagorean win total will not be captured here.
Most of that is improvement in the bullpen, less because the new guys are so good, but because last year's group was so bad that it's statistically unlikely that any group of major league pitchers will repeat that performance.
Here are the detailed individual projections:
*If you're not familiar with wOBA, it's a composite offensive value metric similar to eQA. That doesn't help you? Sorry. Here's how to think about it: wOBA adds together all a players offensive contributions and then translates it to a 0-1.000 scale weighted like OBP. So about .330 is average, .365 or above is good, and .300 or below is bad. If you scan the Nationals team page on Fangraphs you can get a pretty good feel for what the scale is like or read more here.
**FRAA=Fielding Runs Above Replacement. There's actually a Baseball Prospectus stat called this, but since I like to be confusing, that's not what this is. As explained above, this is my own calculation of the three-year average of the player's UZR runs above average, regressed to the mean to correct for statistical noise.