I've ordered a lot from DealExtreme, probably 300+ orders and they all came fine. Sometimes it takes a while for them to process your order (back in February after the Chinese New Year people were waiting like 3 weeks) but it seems to be okay now. I ordered 10 earphones from them at ~$1.50 each (and they aren't that bad either) about two weeks ago and they arrived yesterday. From what I've seen, they mark every package with around the same amount for customs, I've never paid duty on any order.
DX is great if you have a bit of patience. Shipping is free worldwide.
DX is very inconsistent when it comes to shipping. It will take at least 10 days for it to get to your house. Sometimes it takes them over a week just to ship it out! It all depends on what you order. I say it's a great value, but don't go there if you need something right away, or if you are looking for a quality product. I do not recommend buying any type of computer component from them, they are (for the most part) cheap (in quality), and could easily break in a matter of days.