Purchased these due to other reviews and positive comparisons found online, have had them about a week, and have just worn them around the house and on a couple quick errands.  As others have said, they are very comfortable.  They do mold to your foot over time, and are already starting to do so from just wearing them here and there.  The arch support is excellent as well, best I've had in a flip flop.  Also, they are wider than other brands (Reef, especially), which is good for those of us with a wider foot.  I usually take a wide or 2E shoe and these fit nicely (though, admittedly, not much room on the sides).  The traction is pretty good on these as well.  Wore them out in the rain to test traction and how waterproof they are, and no issues.  Looks like they were never wet.  Strap isn't tight either, and I have a tall foot and high arches.  Fits nicely without rubbing.
With that said, there are some minor issues.  They look nice, but are a bit on the clunky side.  Not a sandal you're going to forget you're wearing.  Length wise, these are a tad short compared to what I'd prefer.  I am a 10.5, typically wear 11's in flip flops, and I am used to some room at the ends.  However, these are closer to a 'perfect' fit in that there's not a ton of room left.  I'm hoping they will flatten/stretch a bit, as most flip flops do.  If not though, they fit well, just not as roomy as expected.  So, I'd recommend considering a size up if you like some space in the back and front.  Finally, if you have low arches or flat feet, I'm not sure these are your ideal flip flops.  The arch support is pretty tall and solid, so it may be more of a pressure point that a cushion to some.  Finally, and this is personal opinion, just not a fan of the cursive 'OluKai' stitching on the strap.  Makes an otherwise manly, sturdy sandal look...well, less so, in my opinion.
Overall, it's a nice, comfortable sandal that should be good for whatever you want to do, weather it's going to the beach (though not sure how abrasive sand will be on there) or walking a few miles around town.