I feel your pain. I had someone last week pay, then I posted within an hour of payment. He got it 3 days before the eBay estimate (from central west NSW to some remote place in far north Qld - took 4 days). I answered questions he had, I sent him a message after I posted, explaining that due to his remote location and the time if year it could take longer than the eBay estimate. He replied and thanked me.

So, for my efforts, he gave me 4 stars for everything. He left me positive feedback, I left same for him afterwards, then I noticed that some of my stars were missing an arm, so I ran a DSR report. Sure enough, 4 stars for everything, including postage time. So, I replied to the feedback he left me, mentioning his ID and thanked him for trashing my stars.

I know 4 stars isn't a defect, but I work damn hard to keep my 5 stars, only for some twerp to go and wreck it. Seems posting within an hour of payment wasn't good enough. Maybe I was expected to post it before he even bought it?

If you haven't left them feedback yet, I would leave it, but mention their ID and thank them for trashing your stars. 

As for buyers requesting/demanding feedback, there are some buyers who will neg you for not leaving feedback first. There are a few on my party list that have done that. The neg will read something like "doesn't leave feedback" and that's it.