Anyway, I just recently made my first purchases on pkmncollectors, too. One from the US and one from Singapore... That is clearly replacing the commonly known and big online auctionhouse for me. Wanna know reasons? I give you reasons:
First, you can see the item you are about to get. Second, it's much more personal. The people are friendly and this makes it easier to ask questions if you are unsure about whatever. ;) Third, it's a good trade system. You have to take many steps to gain sales permission in the community and usually get feedback for every purchase (or sale) you're doing. Bad members are banned. ^^ Fourth, it's mostly cheaper. I think I could tell more points, but these are the main ones for now.
Okay, I'll be going out now. Such great weather for March here in Germany, 20 °C (68 °F)! :D