I own a 3, but not the Plus (the Plus in my profile is the older, white waterproof one).
The 3 was pretty bad for a while. The software was buggy, sideloaded books would take a long time to show up. I believe that's the reason for the low ratings.
There was a software update a month or so ago that seems to have fixed most (all?) of the issues. The device seems faster too. I have been happier with the 3 since the update than I was since I bought it.
If you get a 3, just make sure to let it update.
I don't borrow library books. I believe you can use ADE to load them.
However, if the library is going to be the bulk of your reading, you might want to look at Kobo (available on
Walmart's website or
directly from Kobo). Kobo devices let you borrow books via overdrive directly on the reader as easily as buying a book from the store.