Using the handy-dandy Trade Value Calculator, the utility of which I've explained here, here's a breakdown of the Beimel trade from a WAR dollar value standpoint:

Joe Beimel

Beimel has established himself as a slightly above replacement-level reliever and will likely deliver about 0.2-0.5 WAR to the Rockies over the rest of this year (I'm projecting 0.3) at a cost of $800,000.

His primary value lies in his Type B free agent status, worth $2.5 million to Colorado. Here's what the calculator spit out given his contract situation and projected future production:

To the Rockies, Joe Beimel is worth about the same as Rafael Betancourt as a trade chip.

UPDATE: The Rockies are only paying $400,000 to Beimel for his services, making Beimel even more valuable to the Rockies. The numbers have been adjusted accordingly.

Prospects

The Rockies gave up Ryan Mattheus and Robinson Fabian, players that weren't even graded by Sickels--basically meaning that they has very little (or, more likely, no) major league value.

Conclusion

This is effectively a salary dump for the Nationals, as they received very little in return for Beimel--who could at least be moderately useful on the field and could be much more useful in terms of a compensatory draft pick. Is Beimel the left-handed savior to the Rockies bullpen, the piece that will put them over the top into the playoffs? Probably not, but he doesn't have to be--he's the sort of final piece that contending teams add to shore up their bullpens.

While the Betancourt trade was a pretty fair swap, this Beimel deal looks like a very clear win for the Rockies. This is a great trade for Dan O'Dowd, who in my opinion should definitely be back in years to come. In addition, the Monforts should be applauded for taking on the salary necessary to shore up the bullpen.