According to the CBO, malpractice lawsuits cost about $24 billion in 2003. Their estimate is that tort reform could save around 25%, making for a $6B savings. But 2003 spending on health-care in 2003 was almost $1.6 trillion — so we're talking about less than 0.4%. Since health-care costs increased about 7% that year, it's clear that "tort reform" doesn't help.1
As Angry Bear says, Bush isn't interested2 in policies that lower health care costs, but I know someone who is.
 A subtle point nonetheless worth making is that the CBO study shows the growth rate in malpractice awards is half the growth rate of health-care as a whole, so tort reform is even less relevant than the above analysis indicates.
 Bush's plan doesn't lower costs, but it is good for HBOs, insurance companies, and the AMA. Of course, it's tough on the poor slob who gets the wrong leg cut off. Compassionate conservatism strikes again.