Excellent e-reader, and (for me) well worth the high cost. I won't comment on the audiobook capacity since I've never used it (& never will). Being waterproof is a nice plus, though I've had no occasion to test it. For me, the main selling points were the larger capacity, the larger screen, and the free 3G in addition to the Wi-Fi. On all these counts, I'm very happy with the e-reader and it meets my expectations.
It's true that the charge doesn't last as long as with other Kindle e-readers, but I expected that based on other reviews, and I've found that enabling Aeroplane Mode except when I'm directly using the 3G or Wi-Fi (a simple one-tap action in the Quick Actions drop-down on the Toolbar to turn it on or off) extends battery life considerably. Most days I have to recharge at least once - but I read for an average of around 10-12 hours per day, so I don't consider that too big an issue. And I have to say that the recharge time is considerably less on this Kindle.
My only other quibble is the lack of a wall plug as part of the package and the ridiculously short Charger Cable. However, I expected these since they seem to be true for all Kindles, and most other e-readers too. The simple solution is that when I buy a cover for my e-reader, I buy a longer cable and a wall plug if necessary.