The biggest advantage to PRS+ is being able to use your own fonts usually without having to convert the book. If the book has embedded fonts, sometimes that can be stubborn to override, but I've really not run into many books where just changing the .css file on the reader didn't change the font. You create a .css file for each font you want on the reader and just switch the font by changing which .css file is used.
There are many other optimizations also. You can assign what functions you want to which keys and a 2nd function for keys when you hold them down, take screenshots of any page or menu. You can change what is displayed on the homepage, browse your books by folders, change how the page numbering is displayed while you read, change whether you tap or swipe to change pages (not a biggy for me, I love original swiping, but others love that option), show percentage of book read, the possibilities are really too numerous to mention, I'm sure others will post with their favorite features.
And it's now incredibly easy to install. Just download the correct version for your reader, unzip it, plug in your reader to the USB cable, double click the setup.exe file and you're done in about 2 minutes, and that's all there is to it. If you have a Mac though, the first time you install it must be done on a Windows sytem. After that you can update other version on the Mac.
Just do it, you'll wonder how you lived without it all this time once you see all the options. For myself, if the only feature was being able to change the fonts though, I'd still be thrilled with it.
Oh there's games also now, which I don't play much, but another option.
And if you go play with the kids, you'll see they've all installed PRS+ on their readers too because it's that easy and has that many great features!
