I really enjoyed it even though I had read all the spoilers. In retrospect, as usual, I'm kicking myself for allowing myself to be "spoiled" ahead of time. (Geoff Johns was right to warn us!) If I hadn't known what to expect, I would probably STILL be gasping for breath right now!
The part where Linda didn't recognize Wally was heartbreaking. And Wally saying goodbye to Barry and fading away was such a tense moment - again, even though I knew that Wally would be saved. That's just masterful writing. I love it when a comic can make you FEEL emotion, and "Rebirth" accomplished that wonderfully.
This comic was great from start to finish. Best of all, it sets the stage for many more great stories to come!
As for the Watchmen aspect, I could take it or leave it. It's very clever to tie it into Rebirth, but I'm not really a Watchmen fan. I read the graphic novel, and while it was definitely original, I wan't that impressed. The DC Universe is a million times bigger than the Watchmen (in my eyes), so using the Watchmen as a plot device doesn't offend me at all.