I've bought quite a lot from ebay but only 2 knives.
I had one serious problem which is documented here:
http://www.bladeforums.com/forums/showthread.php?t=657645
Thankfully paypal buyer protection worked in my favour and I was refunded the full amount. I didn't check before, but I will be checking the good the bad and the ugly in future before Im make paypal payments.
Stuff I always do:
1) check with the buyer if they will ship to your location - some buyers won't ship "foreign" (i.e. outside the USA) but don't state that in their listing - presumably they're not aware of the rest of the world exists until someone wins their listing. Also many buyers only list US shipping but are more than happy to ship internationally - again I suspect they hadn't really considered the non domestic possibility. So its worthwhile checking either way.
2) I make it clear that I expect and am happy to pay additional shipping and insurance. I'm not sure why but some buyers have been outraged that I would request to have them ship overseas - but then were really happy to do so once made it clear I expected and was happy to pay extra shipping.
3) I always ask them if they are willing to ship using the shipping method I prefer and if they will get insurance. I'll still buy if they use a different shipping method, but I won't if they won't do insurance - I've no idea why some people won't buy insurance, even after i make it clear that I'll pay for it. However if it is a high value item then whatever shipping they use, I want tracking.
4) The legally binding contract business on ebay seems to be one way - in favour of the seller in my experience. I've won items for really low prices, then the seller has reneged and claimed a listing error, in one case after asking very specific questions that clearly identified the item so I don't see how it could be a mis-listing. Ebay did nothing when I appealed. I don't know why sellers don't use a reserve if they really have a minimum price in mind, but it really annoys me.
5) Depending on what you are buying I don't mind if the seller uses a stock photo. If they are basically a retailer and sell lots of that item I think a stock photo is OK. But then again say your buying a custom or semi custom/botique blade, then I'd expect several good photos, especially covering any mars, scratches etc.
6) Read the listing, bidding and shipping section of the listing very carefully. For example I've been looking at cameras lately and Nikon sell bodies with lense kits, that come with Nikon lenses. Other retailer sell the bodies with lense kits too, but not nikon lense kits. If you did not read the listing carefully you might not work that out.
I think feedback is useful, but don't begrudge a seller one or two bad feedbacks out of hundreds or thousands. Some buyers have very unreasonable demands and will give bad feedback for virtually no reason. I usually read the comments too as these can give an indication about whether poor feedback is justified or not.
As for shipping, I'm in Australia and I have always been happy with the US post office services (USPS) Express Mail International. This includes insurance up to $100 and online tracking. For me this was a happy medium between good delivery time and reasonable pricing.
I live in a medium sized state capital (Adelaide) and it usually takes 4-6 days to get from the US to my doorstep or office. That usually costs $30-60 for a big knife/small sword.
Usually the longest part of that trip is from where the package lands in Australia (usually Sydney or Melbourne) to my delivery address. The Express Mail International includes online tracking and insurance up to $100 with additional insurance available for around $1.50-$2 for each additional $100 of coverage.
I.e. USPS seems to be very efficient.
For general USPS info on international shipping:
http://www.usps.com/international/sendpackages.htm
Some of the products refer to country groups to work out which postage rate applies to you. You can find your country's groups and weight limits here:
http://pe.usps.gov/text/imm/immpg.htm
USPS Postage calculator:
http://ircalc.usps.gov/
USPS international mailing manual:
http://pe.usps.gov/text/imm/welcome.htm
The USPS international mailing manual has per country info, info about rates, delivery times for each type of mailservice etc etc. Pretty much everything you need to know, if you can be bothered going through it.
I've not had to use it but I always get insurance with my shipping.
I figure that for a couple of bucks, it is money well spent when you are buying hundreds of dollars of good.
I also strongly suspect that having a trackable package might reduce the incidence of lost packages. I always make sure I get a a tracked package and have not lost anything. I have friends who have saved a dollar or two and tracking and their packages have not turned up. It might be simple co-incidence, but it gives me some piece of mind.