Unlike my competition, I like my hacked Sony Reader Wifi. It's both one of my favorite ebook readers as well as a favorite Android tablet. It's not the best tablet in its price range, but hacking it to reveal the underlying Android adds enough useful features that I think this is easily the best premium ereader on the market.
Assuming this price sticks around, we're going to see the K4 selling for $109 , the Nook Touch selling for $99, and the Sony Reader Wifi for $129. Given how much more the Sony Reader Wifi can do than the K4, I'd definitely go for the Sony.
But you might want the Nook Touch, which has also been hacked and is going to sell for $99. I'm still sticking with the Sony because I like the physical buttons and the overall design. The Nook Touch feels like a toy while the Sony Reader wifi feels like a tablet.
On a related note, I'm going to be at the Nook event tomorrow morning and I plan to liveblog the launch of the new Nook Tablet. You'll get the already leaked news live, as well as any details that B&N haven't already let slip (3G permitting).