macOs Mojave???

It should be fine to upgrade

 

I have the same iMac (late 2015) and Mojave works great on it.

 

I'm on Sierra on my 2015 15" MBP. I'm really excited about Dark Mode and the screenshot functionality - it's seems really nice to quickly record your screen.

Other than that.. Sierra is perfectly fine for me, but I do think I'll try Mojave out

 

Do you know if it's easy to downgrade if I'm unsatisfied with Mojave? I got Sierra backed up with Time Machine - would it be easy for me to install Mojave, and if I were to really dislike it, restore back to Sierra from Time Machine? I checked some youtube clips and it seems like a hassle

 

You might want to hop on a search engine and check out the features of Mojave versus those of High Sierra. That said, I am running Mojave on a Mac mini Late 2014 machine and it runs rather well.

 

Only you can answer that. Take the advice from the poster above and look up the features.

 

I'm glad that's over... The question should be, Why shouldn't I upgrade to the latest OS. Many Mac users I know have sophisticated hardware/software and those companies struggle to stay current. Many users are stuck in High Sierra. Virtually all users of recent Nvidia video cards have no drivers for Mojave, and two photographers who use CAP-1 haven't upgraded.

On the other hand, when my 2009 MP was eliminated for Sierra, I struggled to find the Apple upgrade solution to 2010 (4,1 to 5,1). I regret not doing it as soon as it was available. My final solution wasn't mentioned anywhere I read, and lets just say it failed for the first "FEW" attempts (long story short). Also, while the requirements for Mojave are large, "Metal" video card, APFS, no RAIDs, etc, I have cloned the Mojave boot to HFS+, used RAIDs and it all works with my original GT 120 video card. ????? I don't expect I will have that luck with the next OS, 10.15. I am currently running running both my 4-core and 8-core with the latest version of 10.14.5 with the latest bootROM 144.0.
Both are booting from NVM2 blades with speeds as fast as 2700MB/s. I can also boot either Mojave or High Sierra from a striped RAID on a Sonnet PCI card with dual SSDs (just under 1000MB/s)

My conclusion is to upgrade to the latest OS a short time after it is released. Right now I am just hoping that I will make the 10.15 OS list. The best thing K1K1, is that you know to come to the MacRumors Forum to get the best answers for your Mac. The gracious geniuses who have guided me through my troubles in the last couple years are the best on the web.