The Earth thing isnt a fault you can aim soley at Tennants run though.
I had the same issue with Ecclestons run.

Back in the day, Baker et al would rarely spend any time on Earth, or in the current era, but since the revamp, both Eccleston & Tennant spend nearly every episode on Earth or in a reletively similar time period!

Personally I like Tennant for all the reasons you guys dislike him!
I like the fact he is more knowledgeable or cocky (depends on how you look at it).
I also like the fact that he has a really dark side, and seems more inclined to kill than any other Doctor, something that if the writers had any sense, could lead to a future possible dark regeneration or even be how Tennant ends his run!

Snarf is shit. His death will be rejoiced!