I love the waterproof features of the Arcteryx packs, and they carry very well.
I have the older Acrux as a excursion, lightweight (40L only weighs 2.8 lbs) pack, Naos 55 as my Packrafting and wet conditions pack, and just pulled the trigger using REI dividend and 20% off on the 65L Arrakis for snow camping, and Alaska trips.
They are very well made (made in Canada), and the Acrux and Naos are completely submergible and in fact could be used as a floatation device if needed. The Arrakis has waterproof zips, and roll top closure so is still very rain and quick dunk proof.
Never, ever worry about things getting wet, even if you take a dunk in the creek crossings which I hate to say has happened to me :)
Zimmerbuilt's Dry Bag carrying packs are intriguing to me as well, and look like the would work, certainly for things like pack rafting