Foundation hospitals such as the Queen Elizabeth in Birmingham have been given a clean bill of health by official inspectors.
But they could face financial problems in the future, and it is too soon to judge whether they are improving patient care, inspectors said.
Foundation hospitals have more freedom than other NHS hospitals, but their introduction was fiercely opposed by some MPs and unions, who feared they would create a two-tier health service.
University Hospital Birmingham Foundation NHS Trust, which runs the Queen Elizabeth and Selly Oak hospitals, became one of the first in the country to gain foundation status last July.
Heart of England NHS Foundation Trust, which runs Birmingham Heartlands Hospital, Solihull Hospital and Birmingham Chest Clinic, became a foundation trust in January.
A review of all foundation trusts was carried out by the Healthcare Commission at the request of the Patricia Hewitt, the Secretary of State for Health.
It found the dire predictions of critics had not come true - but healthcare had not improved either.
In a report published yesterday, the Commission said there was no evidence to support fears that trusts would poach the best staff, or avoid patients with complex conditions.
However, they also warned that in some trusts the roles of the governors, who are elected by patients and the public to keep the trust accountable, were unclear.
And they said there was no evidence so far that foundation trusts were improving the quality of healthcare faster than other trusts.
Last night Mark Britnell, chief executive of the University Hospital Birmingham NHS Foundation Trust, said the trust's financial position was sound and secure.
But he said it would like more freedom from Government targets, which may not coincide with the needs of patients.
"For example, we have the largest renal unit in the country. Black and Asian people are disproportionately likely to suffer from renal failure, and there is a high demand for this service," he said.
"But it is not a core target of the Department of Health."