I've been on eBay for what feels like an eternity... but what in reality is about 10 years. I've got a feedback rating of 315 - 100% positive. I don't think I've ever had a negative feedback, ever. Though I think I may have had one neutral from some douche who didn't know what he was doing - but that was a long time ago.
I wouldn't say I buy and sell a lot... but I know where to look when I want something or have something to get rid of. I've applied a lot of common sense and logic to my auctions - both buying and selling.
Frankly, I only deal in Buy it Now offers - when both buying and selling. I don't care too much about getting absolute top dollar for my sales so I will usually look up completed listings and see what things have been actually selling for and then compare those for current listings waiting to sell. Then I undercut all of them by a few $$. Bam, item sold.
I have a good example from yesterday. If you've been following along, you'll know that I recently purchased a battery pack for my iPhone. IMO, it was crap. I just wasn't satisfied. So I used it for my trip and planned to get rid of it when I got home. Got around to listing it last night.
I think I had the auction up around 6pm. They're like $80 new... decided on $50 with free shipping (this is another thing I like using - include shipping - people like that).
Woke up this morning and it was sold already. Awesome. Since I keep a stash of padded bubble envelopes, I packed it up, printed a label, and dropped it in the outgoing mailbox at work. Done.
Listed to sold to mailed in about 14 hours. I'll take it.
Sure, I could have probably squeezed out a few more $$ - but honestly when I sell on eBay it is more to get things out of the house than to make a huge profit. If I can give someone a good deal, while picking up a few $$ in the process, lucky them. Hopefully this guy likes his case more than I did.