I know that string theory is still under heavy development, and as such it still can't make predictions (or not that many predictions anyways).
On the other hand, it is clear from the number of years this theory has been under development and from the large number of theoretical physicists studying it, that it is considered a good and viable candidate as a quantum gravity theory.
So, what is the evidence that this is true? Why is it considered such a good candidate as the correct quantum gravity theory?
Without wanting to sound inflammatory in the least, it has been under heavy development for a very long time and it's still not able to make predictions, for example, or still makes outlandish statements (like extra dimensions) that would require a high amount of experimental evidence to be accepted. So - if so many people believe it is the way to go, there have to be good reasons, right? What are they?