I dunno, there was a fair bit of jumping around and talking very quickly in his big 'Power, POWER' speech. It's also pretty awesome how he tells everyone to shut up when he's thinking. (Reminds me of McKay from Stargate Atlantis)

I really don't see how you can say the series has turned into more of a joke. The villains so far have been pretty serious and a lot more well thought out than some of Tennant's episodes (see: Fear Her, Love and Monsters, Unicorn and the Wasp)

Generally though, when I watch the episodes a lot of the time they are suited around the actor's style. eg: Tennant could never act the Eleventh Hour and neither Matt Smith nor Tennant could do The Empty Child.