Asus could be advantageous right now because they currently have proprietary software in SmartDoctor capable of ramping up the fucking retardedly slow default fan speed. You can flash to the Asus BIOS and use the program on any card, but that's a pain in the ass.
since they are all reference designs at the moment and all the same price, go with lifetime warranty. i know visiontek has it from firsthand experience; i have a 3870 from them and it's been great (an aside: i have one of the first run of visiontek's 3870s, which are ATI-branded cards). from the other posts above it seems powercolor also has lifetime warranty.
Reading through the posts it seems pretty clear which companies offer the best warranties. What I would like to know is which of the companies has the best tech support if you call in, and which ones have the best and most efficient RMA policy?
I should add that the only other ATI card I ever owned was a 9800 Pro (I don't even know what company it was) and fortunately I never had a problem with it. Since then I have been using Nvidia cards so I know about them. With ATI I have no clue who to go with.