I purchased this monitor about a month ago and I've had no problems whatsoever with it. I do know what you're referring to and I also read many of those reviews, too. I also read raving reviews about it, too, as well as seeing this monitor received many awards from different rating agencies. What I came to conclude is something I think is true for all high tech items. There will always be some % of products that have issues, this is seemingly unavoidable. And those who do receive a flawed product are far more vocal than those who are happy with their purchase. By the same measure, each and every Nikon camera has some level of noise on the internet claiming it's the worst camera ever made and you should avoid it at all costs. And from their perspective, I'm sure it's true. But in reality, I suspect in nearly all cases, this is a very vocal minority. In the case of the U2413, I doubt it would have received the kind of accolades it has garnered if it was indeed a poorly manufactured item. In addition, Dell offers a full 3 yr warranty on the monitor just in case you do receive a bad copy. Given this, I decided to roll the dice and so far am very pleased with my choice. The nice thing about the Dell warranty is that they'll pay the shipping costs to have your monitor fixed and/or replaced.
So to answer your question, I've seen none of the issues with this copy that I read in the many reviews on line. It could be in 6 or 8 months from now my opinion changes but I still have the option to return the unit at anytime over the next 3 yrs. In addition, because I bought the monitor with a Discover card, in theory it will double the manufacturers warranty (I've never filed a claim for such a thing but I'm told by Discover that it's possible). At any rate, it's good that you're doing your DD so that you can make an informed decision.