First of all, I love the discogs marketplace. It's pretty much perfect for someone like me who is looking for very specific releases and don't really have a lot of local record stores to rely on. The only real downside is the PayPal fees usually added by the sellers (not their fault obviously). I live in Sweden, and I love ordering stuff from Germans. Not only is the Deutsche Post rates very affordable, but many German record collectors / record shops keep their records in excellent condition. And depending on the records you're looking for, and how anal you are about getting specific editions, you can get a lot of cheap copies from Germany because many many US/UK records over the years have been pressed in separate German editions. It is/was a huge market. Same goes for Scandinavia, the Benelux countries, and so on.
But I've also ordered records with great success from serious collectors in Belgium, Holland, Italy, England, the Czech Republic and Austria. Nothing from the US yet. Shipping rates and so on. It's fun in a very nerdy way to browse and notice subtle differences between sellers from different countries (not to mention the 'story' behind the collection that's being sold -- raided fleamarket, old DJ, small record shop, etc).