DealExtreme (DX) is a retailer in China - you're the importer when you order there. KaiDomain (KD) is another just like it.

DX and KD are reputable as to their part of things, but the products they sell are mostly Chinese junk, stuff that couldn't even make it into Wal-Mart in the US. Some items such as many lasers are hazardous, not legal for you to import, and don't meet claims anyway. Nothing has to perform as advertised since they're overseas, but DX and KD will often mark a product page as having suspect claims when people complain (the false claims remain).

UltraFire is a second-tier flashlight manufacturer in China (Fenix is the best of the Chinese makers). Most UltraFire lights are junk, worth no more than the DX/KD price, but a couple in the past have been good deals. It sounds like this one may be too. However, I would avoid putting the water seals to the test by dropping it in a puddle, etc.

SureFire lights are quite a bit more expensive but more reliable in bad environments or under rough handling. That's also the case for other USA makers like NovaTac, HDS, First-Light, etc. These guys also are fully American-made (a lot of buyers care about point-of-origin).

Most American makers focus on durability and bad environment qualities since those are hard to do and bring a premium price. The low-end Chinese makers usually focus on output/brightness since that's easy to do (it's easy to break into the market that way).

PS. A quick note that SureFire's 2008 catalog has been posted and it's clear they have been quite busy in product development.