Its mostly a gimmick in the sense that youd have to work around it to get desired results. I personally dont have nearly the depth to accommodate multiple curved monitors in a single setup. Your experience with flat monitors is just that, your experience. Ive never once thought my viewing angle is wrong with either of my two monitors, its comfy and flat enough to not take up precious space.
In my opinion, curved is great for ultrawide, single monitor setups.
If youre going multiple panels, Ive always liked flat better. Like I said, I cant recommend it, never said other people wont like it.
No such thing as "mostly gimmick" either something is a gimmick or it is not, and implies an item/idea/etc is useless and serves no purpose other than attract attention (shiny). Even if a device serves a small purpose it is not a gimmick, and the term your looking for is niche. I literally laid out multiple use cases where a curved monitor is better that flat, so I'm not even going to classify this as a small niche, but a large one!
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I cant recommend it, never said other people wont like it"... wait, you "can't" recommend something to people who would "like" or benefit from it simply because it doesnt fit
your use case? So if someone came to you and said, I have a problem, multiple flat panels dont look right and I'm constantly having to readjust the angle, etc... your reply would be: "there are these curved monitors that would solve your problem and work perfectly, but I cant recommend them because I dont have the same issue/opinion as you." Here's another analogy; what is a good FPS game; BF5, COD, MOD, etc, etc, etc?; and your reply would be: 'I don't recommend any FPS shooter games because I play RPGs.' WOW, just WOW; you do know what narcissus is?
I am an engineer, my job is to provide solution to meet the needs of our customers. I develop solutions and make recommendations all day long that dont fit my personal use case, you know why... because my personal use case and my customers' use cases may or may not be the same. A recommendation is NOT for you, its for others and to across the board make a statement like you dont recommend something based on your own personal opinions and uses is wrong.