"You look Time Lord."

He kills about as much as he always did, so it's not that

I don't know that it's 'bloodthirsty'. Ten, Nine, Seven (Minus Skaro), even Six (and the rest) all had "What have I done" moments when it came to killing. Killing was always the last result and with Eleven it certainly appears to be a 'first choice'. And in "Day of the Moon" he certainly seems to enjoy blasting them all to bits.

I think what it reminds me of is a 11 year-old who just got the newest GI Joe (yah, dating myself - shush) action figure and is having all kinds of fun blowing up all the other action figures (and Barbie dolls) he can get his hands on.

I don't know what you call it when it's 'real' and quite a bit ooc for him.