There was clear change in Doctor Who quality, when Moffat took the helm. Before Moffat, there where many interesting supporting characters (whom many died, and they were sad deaths). But in Moffats time there has not been a single death which had a meaning. Yes, Moffat has killed Amy, Rory and Doctor god knows how many times, but always used Deus ex machine to bring them back.
I'm really sad Smith had to take role as Doctor same time as Moffat became showrunner, because quality of scripts collapsed. Much of the Flak Smith (which is not very much) is Moffats fault.
Example of Moffats genius: Pandorica opens would have been a perfect series end. Doctor would have been in box for few thousand years and gotten out somehow, and regenerated to new doctor, who is nearly insane because of what happened. Instead, what happened in The Big Bang? Total chickening and stupid cop out, which undoes everything which happened in previous episode. It's like Moffat realized he had written himself to corner, and just wanted really easy way out, so he pressed reset button, so he can write something more interesting. Series 5 and 6 have really woken then Moffat hate in me. I really hope he won't write a single Who episode ever, and is sacked from showrunner position.
And yes, Moffat wrote some good stuff in RTD time. But nothing good DW stuff since he also became a DW showrunner.