The M1 chip seems to be great for what it is, but Apple really needs to demonstrate that they have more than one chip in their repertoire. As it is, Apple is starting to simply make copies of the same computer in different-looking cases. The MBA, 13" MBP, Mac Mini, iPad Pro, and now M1 iMac are almost identical apart from their form factor.
A real chip manufacturer has multiple products that explore the price/clock speed/cores/feature set/power consumption landscape and can be matched to use case. The M1 kills it for an ultrabook, but is only okay for a business desktop and fails for anything that needs significant graphical power.
I was really hoping that the new iMac would have started expanding the landscape that Apple covers, but no such luck. Because of this, I see no reason to get one over a Mac Mini, because it literally offers nothing else of value -- same performance, same IO, same memory and SSD limitations. At least with a Mac Mini you're not required to throw away a pricey monitor when you want to upgrade the computer, which will become obsolete much more quickly than the monitor will.
The pessimistic side of me says that this one-size-fits-all approach is typical for the Apple of the last decade. But I still want to hope that the higher end MBPs and iMacs will start to change this.