Seriously, I'd just let it go. Ebay aren't going to remove that feedback because it's the buyers opinion of the transaction. You gave a good reply, without being a psycho about it (trust me, some replies are just horrid!). 99.9% of buyers won't have a single issue with you having 1 neg. Heck, they'll buy off Chinese sellers with thousands of negs!
Me personally, I wouldn't even bat an eye at that neg. What would stand out to me is the reply. You were polite in your reply and that means a lot to so many people. Some sellers go into an abusive rant and it wouldn't matter how much I wanted their item, I wouldn't buy it. I want to know that if there is an issue with the item I bought, the seller will be professional about it, not abuse me and call me every name under the sun.
Most of us have had a neg, whether it's deserved or not. Yours has already fallen off the first page. It always sucks when you get one, but it's not the end of the world. It will be gone in 12 months and any buyer who looks at your feedback can see that pretty much everyone is happy with their purchase.
As mentioned, I wouldn't send a feedback revision request. Your buyer will ignore it and it will be a waste of a revision that you could use at a later date.
Chalk it up to experience. In a couple of weeks, it won't even bother you. Remember, it's only a coloured dot on a screen.
