See I liked the fact that Tennant has this kinda happy wackyness, but at the same time is a bit of a vicious bastard who also plays great mind games.
The way he killed that alien dude in the christmas episode was quite vicious & the trick he played on the prime minister showed what a great manipulator he is!

I think he is very much a guy who you might think twice about crossing, and you'd never fully trust him!
Of course I havent had a chance to see the new episodes so I dont know if they have expanded on this more!

Oh, and I did watch a bit of an Eccleston episode a month or two ago, but I couldnt really judge it as I only tuned in half way through, and it was mostly about Rose (she was having sex with a Dalek).

Snarf is shit. His death will be rejoiced!