ATW said:. If I lean my head slightly to either direction, the details in the dark areas become more dinstinguished, and the color drop-off at extreme angles doesn't seem too significant to me, although it may to someone else. I'll probably try and get another one cross-shipped and try my luck one more time, and just keep whatever I happen to get.
Simply put, if it doesn't bother you keep it, and stop worrying. I would estimate that less than 10% of people have issue with the shifty nature of these panels(sort of like rainbows on DLP). Use it for everything you plan to use it for, for a week and if it seems fine keep it.
I bought my first panel when I thought they were all the same(both S-IPS and PVA list 178+ viewing angles). I got a PVA Dell 2405. 10 minutes into using it, it was driving me nuts with the tone shifting. I honestly couldn't stand using it and sold it after a week. Next was an S-PVA 2007fp (supposed to be S-IPS, damn lottery) and the same effect. I returned it (It also had banding/blur), next I tried a cheapo 17"TN screen that I still have. It doesn't bother me at all, because it doesn't shift horizontally like a VA. (most annoying and pronounced effects are from the horizontal shift).
Dell is right in thinking they can get away with this swap because the majority of people won't notice the difference. Though for the minority who can't stand this type of panel, this swap is a huge deal. For those of you thinking you need a S-IPS to compare with, then obviously you are not suffering the grief this panel type gives to a minority of users, and for you the panel type is no big deal.
Though I still think for everyone, dell should be clear about what we are buying and not ship us a random product.