I haven't played around with a Kobo, so I can't talk about it. But for work I played with the newest Sony for a week and a Kindle Touch for about a week after that. I love the Sony, and was annoyed by the Kindle. The Kindle just wasn't working as well. The Sony was just a better device.

I read LJ and DW on the Sony and posted comments with no problem. I read from AO3 on it and it worked just fine.

Between the Kindle Touch and the Sony wifi touch, I fully recommend the Sony. I can hesitatingly recommend the Kindle Touch, but fully recommend the Sony.