Using "to my mind"
It means in my opinion and is common in both BrE and AmE. OED and NOAD both give the following description:
to my mind in my opinion: this story is, to my mind, a masterpiece.
And I don't see anything informal with the expression. Neither NOAD nor the OED marks it that way.
As an American, I would never use 'to my mind' in the initial position in a sentence. I often find that German students have a tendency to do just that. Otherwise, I use it more to mean 'in my opinion', as in "He's got pink walls and a green carpet, which to my mind, looks completely wrong."