A lot of my friends and I are going about it in "ultra hard mode". It consists in having to use the guessed letters (that's normal hard mode) and always using the last day's word as your start word. It makes it really fun and really challenging.
What I don't like about "hard mode" is that it removes one level of strategy. If I for instance realize the word could be CRATE, CRAVE, CRANE, CRAZE, it feels "harder" to figure out a word with T,V,N,Z to guarantee a guess in two, instead of just trying all four since I need to use the already found letters.