Sorry, "I've tried" is not really authoritative. I appreciate your opinion but it doesn't portray an accurate picture of the iPad reading experience. "Heavy" is a non-issue. I have countless hardcovers that I've read through the years that I would consider heavy, but I, and others somehow managed to read them. I simply can't think of any situation where I've held my Kindle freely in the air while reading. It's either angled on an airline tray, sitting atop my laptop bag while riding the train or in my lap while sitting or reclining. I've never though "my, this is so lightweight I'll just hold it out in front of me or over my head." That's just not how I read. I understand that you may be different, but not once in 3 months of reading (easily a book a week, sometimes 2 - let's say 1.33 X 12 = 16 books) has the iPad's weight ever been an issue. And the backlighting freakin' rocks in bed or on a plane.
One more thing, while "most novels don't have photos" the novel is just one segment of the book market. I read lots of non-fiction and there's plenty of photo (and map) content there. Even in a novel like "The Girl with the Dragon Tattoo" there's both a map and a family tree. They don't look very good on the Kindle. I'm much happier getting 100% of my reading experience over the 90-95% I had before.
There's clearly room in the world for both types of devices, but you really can't dismiss the iPad's effectiveness in the e-reader category.