At this point there's little doubt that CBO is coming under attack from health care reform proponents for its analysis.
For example, take a look at this column by Bruce Vladek in yesterday's Roll Call. Although there are many, here's what I consider to be the money quote:
...CBO’s track record in predicting the effects of health legislation is abysmal. Over the last two decades, the CBO has routinely overestimated the costs of expanded government health care benefits and underestimated the savings from program changes designed to reduce expenditures.
This is actually a debate that's been raging for weeks in a variety of ways within the budgeting community. I received a lengthy e-mail several days ago from a friend and budget scholar (whose name and material I don't have permission to use) that went into great detail about this. That's typical. After all, a discussion on estimating techniques is the stuff that dreams are made of for many budget wonks.