Amazon recently released the 4.1.0 software updated for the base $79 Kindle.
There are a number of performance enhancements, but it looks like (literally) the best improvement is the new reading font - most of the reviewers say that it’s far clearer and sharper than the old one.
Anyway, if you have a $79 Kindle, the upgrade looks like it’s well worth it. Directions for upgrading are at the Amazon link at the top of this entry.
-JM