You can always bash something and praise the other thing like crazy. Nothing is perfect, and so does iMac.
If I want to bash iMac, I could do it easily too, you know? Owning something like an iMac is like having a sexy computer, but no matter what, you're risking all your eggs in one basket.
A generic cardboard computer tower is easier to maintain, also cheaper to fix and upgrade. And in my experience, PC components could come with better support so that you don't care too much if it devaluates quickly.
For example: I could get 27" Dell U2713HM display (it's 27" and 2560x1440 too) for $700 and it already come with 3 years warranty. No AppleCare needed. While it's made of plastic and might not as sexy as an iMac or Apple Thunderbolt Display, it works great with both Mac and PCs (ironic, huh?) and having multiple inputs is a breeze.
One simple thing breaks inside .. and ...
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The ugly cardboard desktop survives 