12 days so far with my Kindle DX Graphite and I love it!
I sold my Nook because I was having problems reading my Oracle and SQL books, screen size issues (plus difficulty finding computer book titles at B&N) But YES, for technical books, books with complex layouts or MANGA, the 9.7 inches screen is really nice, way much better than a Sony or any other eink device, like Nook.
I downloaded a Manga the other day, a sample one from Amazon, and looks okay. Some pictures were kind of dark, and you have no color, black and white only, of course. It was also slow turning pages but I see same behavior when reading PDFs; I am sure this will be fixed with next firmware upgrade so would not worry too much about it.