[tikwidd]

You could try giving a choice of two or three letters that the user selects to make it a bit easier to form words. Or the block could cycle between several letters as it drops and the letter gets decided when it hits the bottom (maybe some blocks could do this?).. maybe wildcard letters too? And it would be fun to turn up the fall velocity on more common letters!

It would also be neat to score words with less common letters higher like scrabble, or map your dictionary to a distribution in an English language corpus and score them based on rarity.