I was fortunate that my high school library had a subscription to Omni from the beginning in 1978. Every month I would pour through its pages, and was invariably entertained and educated. It was a mix of hard science, science fiction, evocative artwork, and pseudoscience such as UFOs. But its glossy pages had enough gravitas to get authors like Robert Heinlein, Carl Sagan, Orson Scott Card, William Gibson, and George R.R. Martin, whose seminal short story Sandkings first appeared in its pages. The work of artists such as H.R. Geiger and Rallé graced its covers.
This was great stuff for someone in the 12-year-old crowd; there was a lot of learning in those pages, but a lot of fun as well. I was already a sci-fi fan, but Omni opened up new worlds of "serious" science fiction, as well as science speculation. I very much miss Omni's unique blend of science and fiction.