No, you do not. You can purchase items from any city you've become a Champion of regardless of your status with other cities.
"I was thinking of re-rolling a new character but with the next expansion on the not too distant future. Would it be better to squeeze every drop of fun out of my main or re-roll and always wonder where I could have been if I only kept going?"
This is definitely a personal choice, and with that said, I tend to get one of my characters really geared up before I start working on another alt. If you're thinking of completely re-rolling, I'd say now is as good a time as ever. The next expansion is probably a year or so away, even though I suspect we'll start hearing about it in the next few months (BlizzCon in August).
"I'm wondering, how long is the Argent Tournament going to be around?"
It is a permanent in-game feature.
"Is there a way to hide the user interface on the character select screen?"
No, but you can press Alt-Z when you're in-game to hide the interface (or whatever you have it set to if you've remapped the hot key).
"I recently noticed patch 3.1 has been making WoW a little bit more demanding with my resources. Now iTunes seems to be using up a bit of crucial memory and I know that there are better music players with smaller memory/CPU foot-prints out there that I can use. Do you know any good iTunes substitutes for playing my music in the background?"
Good question. As Riley said, check out Winamp. It really whips the llama's ass.
"Here's a question for the Queue...not necessarily game-related, but why don't you ever post anything like "Congratulations to (user name) for winning the (contest)" whenever you are holding a "post your comment for your chance to win"?"
Most of the time there is really no compelling reason to post randomly selected contest winners. However, some of our other, larger contents, like the recent artwork one, will get a post showing off the winner.
"On the WotLK soundtrack, there is a track called "Forged in Blood." I'm certain I've heard several of the motifs used, but I just can't place where. I also haven't heard where the second half of "Rise of the Vrykul" plays in game; I know the first half is used in both Utgarde Keep and Utgarde Pinnacle, but the second part (with the choir singing part of the main theme of WotLK) eludes me. Are these heard anywhere?"
This is a great question, and one that I have absolutely no answer to myself. However, hopefully some others here will have an answer and be able to provide some input in the comments. The music of WoW is truly amazing. Before I came to WoW Insider I worked as an operations and personnel director for a symphony orchestra, and the lengths that Blizzard goes to orchestrating and producing WoW's soundtrack is astounding. There is a nod to the fifth movement of Berlioz's Symphonie Fantastique in the loading screen's music that gives me chills (and horrific memories of producing the concert) each time I hear it.
Have questions about the World of Warcraft? The WoW Insider crew is here with The Queue, our daily Q&A column! Leave your questions in the comments and we'll do our best to answer 'em!