The first reviews have now been published before the first orders reach customers on Friday. This means that the embargo has been lifted. These reviews give us a first look at the colors of the iMac in the real world, as well as the completely new, ultra-thin design.
As expected, the performance of the new M1 iMac is similar to that of the previous M1 Mac mini, MacBook Pro and MacBook Air. The Verge expressed as follows:
Another way to interpret these numbers is that I effectively got the same performance out of this machine as we got from the M1 MacBook Pro and the Mac Mini. That's not surprising, since those machines all use the same processor. But it's a good guide to judging whether the iMac can handle your work: If you expect to be able to get a task done on the M1 MacBook Pro, you should be able to get it done on this machine. Anecdotally, I was able to use my review unit for all kinds of daily tasks, from emailing to YouTube to amateur photo and video work. I was able to jump between more than 25 Chrome tabs while Cinebench ran in the background without any stuttering or slowdown. If you're buying the iMac for these kinds of tasks, I can't imagine you'll see too much spinning wheels.
Engadget describes the new design in detail, focusing especially on the orange option:
I chose the orange iMac for our review. Apple probably should have just called it Creamsicle. It has a slightly pinkish tint along the "chin" below the screen, while the rear casing looks more distinctly orange. And despite the playful aesthetic, the iMac still looks and feels like a premium machine. I especially like the way light bounces off the back of the sturdy base. The iMac hasn't had this much power since the days of the G3. Hell, Apple could still benefit from borrowing a few design ideas from that long-forgotten machine—or maybe I'm just the only one who misses being able to adjust my screen vertically.
iMac 2021 is available in seven different colors
On Six Colors Jason Snell has some good descriptions of what it's like to work on a colorful iMac, especially with the white bezels:
When you sit down to work on the iMac, you get a different impression. The bright color is there, visible on the stand. Above that is a more muted version of the accent color on the "chin" below the display. The bezels around the display itself are a neutral gray. It's effectively a gradient where peripheral vision picks up the bright color but that accent fades away until what's left is what's visible on the display itself. It works really well, although I imagine it's quite a dramatic contrast if you're someone who prefers Dark Mode in brightly lit rooms.

The Wall Street Journal summed up the whole thing together in a particularly sympathetic way:
In that sense, the iMac's evolution into the future - and into the family of iPhones and iPads - isn't quite complete yet. I'm looking forward to the 2030 iMac review: the friendly, fun home computer is thinner than paper, has no ports or cables, and can beat a 2020 supercomputer at any task. Oddly, it still has a mouse that needs to be flipped over to charge.
In a nod to the original iMac G3 from 1998, the new iMacs are available in a range of new color options, including green, yellow, orange, pink, purple, blue and silver. The new model is available in three versions. Prices start at 1,449 euros. So if you want to order a device, you can do so via Apple's website. (Image: Apple)