In Letterpress, how does scoring work? Do I earn more points for certain hard to use letters, or for letters which are dark blue (all mine)?
It's a straight up one point per letter under your control. If you flip a letter away from your opponent, it's both +1 for you and -1 for them, a net swing of two points in the overall score.
Darker tiles aren't worth more - a darkened tile signifies a 'block' - if you control all the letters surrounding a letter, then that tile cannot be flipped until the tiles around it have changes hands. While your opponent can use that letter to form words, they will not gain control of it by doing so.