I have a Kindle Paperwhite 2 and I love the new upgrade. Not noticed changes to that font, but I only use Bookerly. The UI changed with this release; options like airplane mode is easier to get to, and everything looks more modern and less boring, without a single negative change to the important thing; reading books. Goodreads integration so it's easy to track what you're reading, have read and will read. It sucks if people are having problems reading a particular font but you can inject fonts into books if you like.
You probably can't get this upgrade if your kindle is that old. I upgraded from one bought around the same time to the PW2 just for the built in light, but between that, the touch screen and the new fonts it's a totally different device.