This sammy issue is pretty much like the "stuck pixel" problem LCDs have... The manufactures will ship monitors that have up to a certain number of defective pixels before considering the panel defective. Some lucky bastards get panels that are 100% functional, others may get several ugly colored dots on theirs - both paid the same price.
The only thing you can do if you want an Xbox with a Samsung drive or a LCD monitor with no defective pixels is to buy them from a store with a good satisfaction guarantee and exchange until you get what you want. MS doesn't advertise the ability to read CD-Rs on the Xbox... I'll admit, as a modder, it's a feature I wanted... Out of the 4 Xboxes I bought, 3 had Samsungs on the first try - the one that didn't, I got it after one exchange.
I do agree with the other poster that if MS were to level the playing field, they'd simply drop Samsung and that would be bad... Regardless of whether or not you hate MS, please don't return Xboxes you've broken the seals on just to swap out a Samsung drive. If MS notices there's a "Samsung Shrink" problem, they'll probably drop them and that'll be it... If you're trying to get a Samsung drive, just buy a new Xbox and power it up - if it turns out not to have a Samsung drive, don't break the seals - just carefully pack it back in the box and return it so it can be sold to someone else who won't care it has a Philips or Thompson drive.