JKR has posted this to her site:

Section: Rumours

The announcement of the publication date on JKR's website was unusually brief. This means that JKR is unhappy about the date.

This could not be further from the truth! The 21st July publication date has given me enough time to write the book I wanted to write, and for the manuscript to be properly edited. These are the most important things to me. An earlier date - eg, 7/7/07 - would have meant that either the writing or editing was rushed, and neither my publishers nor I wanted that. Any brevity in my announcement was down to the fact that I was busy editing!

See it here.

JKR has entered a Diary Entry on her site. It reads:

Section: Diary

FEBRUARY 6th

Charles Dickens put it better than I ever could:

'It would concern the reader little, perhaps, to know how sorrowfully the pen is laid down at the close of a two-years' imaginative task; or how an Author feels as if he were dismissing some portion of himself into the shadowy world, when a crowd of the creatures of his brain are going from him for ever.'

To which I can only sigh, try seventeen years, Charles...

I always knew that Harry's story would end with the seventh book, but saying goodbye has been just as hard as I always knew it would be. Even while I'm mourning, though, I feel an incredible sense of achievement. I can hardly believe that I've finally written the ending I've been planning for so many years. I've never felt such a mixture of extreme emotions in my life, never dreamed I could feel simultaneously heartbroken and euphoric.

Some of you have expressed a (much more muted!) mixture of happiness and sadness at the prospect of the last book being published, and that has meant more than I can tell you. If it comes as any consolation, I think that there will be plenty to continue arguing and speculating about, even after 'Deathly Hallows' comes out. So if you're not yet ready to quit the message boards, do not despair...

I'm almost scared to admit this, but one thing has stopped me collapsing in a puddle of misery on the floor. While each of the previous Potter books has strong claims on my affections, 'Deathly Hallows' is my favourite, and that is the most wonderful way to finish the series.

See the "Text Only" Version here.

I'm encouraged by her admission that DH is her favorite book. I'm hoping it will be mine too.