I have to agree that it depends on what you sell.
Tuesdays and Thursdays seem to work well for me but my "micro" testing is hardly conclusive.
Ebay recommends Sunday nights, because that's when the most people are Ebaying, but Sundays don't seem to do all that well for me. I've read that most sellers list on Sunday and wonder how much that thins out the buyer market.
I've heard that 5-6 am is best for railroad collectibles because that's when most retired engineers, still in the habit of rising early, are on Ebay shopping.
I've also heard that noonish Wednesdays is good for business products.
When I first got started I read that most North Americans do their overall surfing between 8-10 pm nightly so I usually list shortly after 8 pm. This is as opposed to UK surfers who principally surf between 6-8 pm. When I was listing slot cars, for which there is a considerable market in the UK, I tried to target the 6 to 8 pm time slot which worked out, I believe, to be about 10 am PST.
This is the type of info I wish we could get from Ebay. Which country buys the most, and when, for each specific product category? It's pretty dificult to figure this out on our own.
Marty