I always leave feedback after receiving the item if buying and after having received feedback from the buyer if selling. As a seller, leaving feedback first has a very big risk of getting an unjustified negative as a lot of bidders can be a bit stupid eg if they misunderstood or didn't read the description and so don't get what they were expecting, or if it gets lost in the post and they think that's your fault, or something similar. There have been a few times as a seller (I haven't had any problems as a buyer yet) that I've wanted to leave negative feedback for people who change their minds after bidding or take weeks to pay, but I never have as they would just leave a negative back even though I'd done nothing wrong - that is the main problem with the feedback system, that a lot of issues aren't reported through it as it's not worth it for the retaliatory negative. There's not much they can do though, as there's no way they can determine which negative feedbacks are justified and which aren't though.
I would have been very unhappy in this case though, as the charge for pickup should have been made clear and that way the buyer has a say if they think such a charge is unjustified (which it is, the seller obviously just wanted to get more money for the laptop than was bid) by choosing not to buy. Of course, you could have refused to go through with the purchase, I'm sure eBay would have taken your side if you'd used the disputes system, but then you would have ended up with an unjustified negative. I guess $15 still isn't a bad price though, I'd like a PPC laptop myself and that's quite cheap
