Some things that could be worked out:
--Don't allow words with the same falling speed to spawn on top of each other; this prevents either of the words from being read, and pretty much guarantees that they will hit the bottom.
--Add difficulty modes; seeing 'disestablishmentarianism' come barreling down the screen at full speed the first time you start playing is really scary.
--Although the long words with strange letter combinations really help with precision, they're not particularly applicable to everyday typing, in my opinion. Helping people to practice on more common words might be more useful.