I just finished putting a new machine together this weekend and ran into a graphics glitch that happens after running the computer for ~1 hour or so. Once the machine reboots the problem goes away. I've even had the screen lock on me a couple times. I took a screenshot to show the problem...
It appears Costco has the best price on Burning Crusade. Its $34.99 which is $5 cheaper than anywhere else that I've seen. They did not have any copies of the Collectors Edition.