They've tried to outdo each previous season in the "big story", and the big story is worse and worse each time. Also, they have been coming up with some awful ideas. I think there are very few episodes I've liked in the past two seasons other than "Dinosaurs on a Spaceship", which still reminded me of "The Pirate Planet" by Douglas Adams (part of the Fourth Doctor's "Key to Time" extended plot). I also liked "The Doctor's Wife", though of course that was written by Neil Gaiman, and not their usual writers.

The problem is that they overuse bad guys. The Weeping Angels were cool the first time, and have lost their coolness with each successive use. It should have been a one-off story with them only, "Blink". Other one-off stories with Tennant were great, like "The Girl in the Fireplace", "Silence in the Library", "The Doctor's Daughter", "Father's Day" and even "The Impossible Planet/The Satan Pit". Those episodes seem to be fewer and farther between with Matt Smith.

And Hell, I just don't think he's as good a doctor as David Tennant was. Tennant gave Tom Baker a run for his money and frankly, in my opinion, beat him in the "Best Doctor" contest. Smith may be better than, say, Sylvester McCoy was, but in the marginal way that Colin Baker was, not the solid way that Peter Davison or Jon Pertwee were.