Rob, I've learned (the hard way, unfortunately) that it really doesn't matter what you say, or what you do. There is just no pleasing some people. And some people will just flat out lie.
I usually ship items the same day people pay if they pay me before around 2pm or the very next day at the latest, since I have no job or anything... and yet, I still can't seem to get above a 4.7 - 4.8 on my DSR scores.
Not to mention that I had a buyer who bought a Galactic Heroes figure from me for like $2, paid, I shipped it next day, she got it in 3 days from the end of the auction. On day 7 after the auction, she leaves me a negative feedback, says it took me 8 days to ship (even though it had only been 7 days since the auction ended) and that my communication was extremely poor.
So basically, ebay sucks. But what can you do?