I agree about the pre-new-age-sitch-debacle Omni, it was a fantastic popular sci-fi magazine. It was greatest for its high quality short fiction and gained quite a reputation having many heavyweight authors published. For a couple of years, having a short story in Omni was of higher prestige than Analog, Harpers, et al.
Then it spiraled down into crystal-rubbing area 51 vegan crap.
The thing I loved about it was that it was about possibilities.
Far-reaching science. Fiction.
One article was about an HP calculator plug-in for betting at horse races. I worked on the math and used it for a couple of years to take advantage of parimutuel descrepancies. Example: you would have made more money betting Secretariat to show rather than win in the final leg of the Triple Crown.
My most-memorable fiction piece was about a guy who had his body tatooed in some exotic southeast Asian camouflage patterns to the point where he could become invisible…
I remember OMNI fondly. It was there I first read Spider Robinson. They printed the second chapter of Mindkiller as the short story ‘God is an Iron’.