I was on the fence for my new iMac (arriving this week.) As far as I can recall I've always purchased it for the Apple laptops that myself or a partner purchased, going back to the early 2000's. (Work provided MacBooks being the exception.) Practically: it has been helpful for batteries which died beyond what was reasonable, display hardware issues, keyboard fixes, maybe a (mechanical) hard drive fix and more than I can probably remember in all of those years. Unrelated to paid warranty I've even had a few out-of-warranty repairs be provided: most recently for the display coating issue seen on some older 2014/2015 MacBook Pro models. The Authorized Service location had my 2015 Pro back to me with a brand new display within a week. The machine looked like new – and it was nice to get rid of that funky purple UV effect around all of the edges.
I've always had solid experiences with Apple and Apple Authorized service, and having Apple Care just makes it so much easier and less stressful to get a hardware issue resolved. Especially for flaky batteries that die well before they should, cycles wise.
When it came to having a desktop I was feeling similar to you because this computer isn't going through the same beating everyday that a laptop would. And it has no batteries. I try to avoid extended warranties generally, preferring to pay for a repair or replacement out of pocket, but for some purchases it makes more sense. (It helps purchasing using a credit card that extends manufacturer warranties as well.)
This is the first iMac I have purchased new and I almost didn't add AppleCare it to the shopping cart.
But in the end I decided to get it: Macintosh repairs can be complicated (thus expensive) and wanted I opted for the ease of repairs should the iMac have a major issue in the next few years. I am of the opinion that most issues will typically show up in the first few years. While some of my Macs have had warranty-covered issues, one has never died on me past the AppleCare period. And many of the devices I've owned I sold or gifted to people in my life, so I've seen how long they've lasted them.
The last factor that pushed me over the edge was the international nature of Apple Warranty. You can get things fixed all over the world. I've lived abroad, travel a lot (pre-COVID) and may one day move again. If this iMac comes with me, I'd feel even better shipping it across the world knowing I book an appoint with any Apple Store should an issue pop up.
One nice new addition in the past year is the inclusion coverage for accidental damage: "Up to two incidents of accidental damage protection every 12 months, each subject to a service fee of $129 for screen damage or external enclosure damage, or $379 for other damage, plus applicable tax" (Canada.)
It sounds like you are already convinced to get it, but I just wanted to share what went into my thinking.
