Again, your sentiments are exactly as i expressed when i first ordered mine. I thought I'd just exchange it for another, not that big a deal. What if that one is also bad? Well, let's think about that later.
Fast forward to today and I've gone through 5. Each one has had a defect and not just the screen. Screen issues ranged from yellow to grey bar across the screen to dead and stuck pixels to excessive backlight bleed from corner. You couldn't watch a movie without noticing the bleed on the bottom black bar. Non-screen issues ranged from no wifi card to grumbling hard drive noise to dents in the stand to high pitched whine when lowering brightness. And of course right when you've returned your yellow iMac, the replacement doesn't have it but instead has a grey bar. Then you think you might go for a repair instead but who knows if it would fix it (what if it ends up worse) and why should you have to repair a machine you just bought. But if you go for repair, you are no longer allowed to replace or get a refund. Also, don't know if you're bothered by dead pixels but every single one i had had them in some form (including the iSight)
Taking into consideration that i had to lug these 40lbs machines to and from work and home and that this took over a month in total, I sincerely wish you luck on your order but keep in mind it could be this bad. Then again, maybe you might have accepted a faulty machine as "good enough". I also had a problem with fedex but that's a whole other story.