Here is wiki's summary of recent investigations. RAND's is the only one with positive findings.
Here is the [RAND's press release] (https://www.rand.org/news/press/2016/02/08/index1.htmlRAND's press release). It does have some positive info, but also states that:
However, waiting times are highly variable by location and type of care and some veterans in some facilities face very long wait times, such as almost 40 days for a primary care appointment at the extreme. In addition, surveys show that VA patients are less likely than private-sector patients to get appointments, care and information as soon as needed.
Reports are linked here. I do not have time to read them, but it is important to check if their comparison is to treatment & outcomes from non-VA hospitals for veterans alone, or for general public. I suspect that compared to a typical US patient, veterans are more likely to comply with doctor's orders, are more fit, and less likely to "complain" in surveys.