I did my first PAD in 2008, missed a few days, but overall, completed it. Continued into 2009, got to about August, before I got very fed up with feeling pressured to take a photo every day. While having 2 young kids gives ample photo ops, it also can really deplete one's general brain, never mind the creative portion of it.
Started PAD #3 in 2010. I managed to delete the Feb 20th pics from the card (and couldn't recover using the Lexar software), so I have no photo posted for that day, though I did shoot, and haven't missed a day yet. I am shooting the "real" PAD where photos are taken each day, and EXIF is always intact.
I do post most days, though trying to keep my 22mos son out of my office while processing/posting can be a challenge on days, so sometimes photos don't go up the day they're shot...........but 90% of the time they do.
Here are the 3 galleries:
http://www.pbase.com/bostonrott/picture_a_day