I got my Oasis about a month ago, with the Walnut cover. I too lose my location occasionally, and can't figure out why. I think I must be accidentally pressing at the bottom of the page.
Anyway, I love my Oasis. I hadn't had a nice cover before, and I love being able to hold it like a book. It is such a luxurious feel!
I had the Voyage previously, and I have noticed a couple of very minor things. The first is that the screen on the Oasis feels silkier. It just has a smoother feel than the Voyage. The second minor thing is that the bottom bezel is narrower than the Voyage. This means when I am on the treadmill, the last line of text almost gets clipped off by the ledge on the treadmill. And when I read in bed, the Oasis is supported on my chest, and the last line is a bit lower than what it was on the Voyage.
Notice I said "minor"....I can still read the last line. It's just that I have to tilt my head down a bit.
The rest of my observations are similar to what others have reported. No adaptive light control, but longer battery life if I leave it in the cover. All in all, I am very happy with my purchase.