Yeah, i've used deal extreme a few times.
There's a good mix of items, some are excellent value for money and exactly the same as in your local shop for 3 times the price.
Others are a load of crap and total junk
Figuring out which is which is just a matter of reading all the comments other people have left about the products.
And also common sense about the complexity of the product verses what they are asking for it.
Most of the time your items ship in less than 2-3 weeks and take 1-2weeks more to arrive but this can vary greatly, especially if you have lots of items in one order since the order waits until all items are in stock. A few times i've ordered stuff that has shipped in a few days and arrived in 1 week. Other times its taken 2 months to ship and another 2 weeks to arrive. So yeah, its very unpredictable, but the stuff does arrive eventually (unless they email you to say the product is no longer available).
When items are shown as "Typically ships in X to X days" Treat that as meaning "We believe we can get this product soonish"
When items are shown as "Item is temporarily sold out." Treat that as meaning "This item won't ship for many months if at all"
I know a few people who have returned stuff and got replacements without any problem.
But i've never had to do that myself.