I'm going to quote a couple of things to back up some of my early statements from FG:
Perhaps one of the most controversial aspects of sabermetrics is the way in which WAR is used. Given the nature of the calculation and potential measurement errors, WAR should be used as a guide for separating groups of players and not as a precise estimate.
League-average WAR rates vary. An average full-time position player is worth about 2 WAR, while average bench players contribute much less (typically between 0 and 1 WAR). Average starting pitchers also are worth around 2 WAR, while relief pitchers are considered superb if they crack +1 WAR.
For position players and starting pitchers, here is a good rule-of-thumb chart:
Scrub 0-1 WAR
Role Player 1-2 WAR
Solid Starter 2-3 WAR
Good Player 3-4 WAR
All-Star 4-5 WAR
Superstar 5-6 WAR
MVP 6+ WAR