Omnibus 1 in my opinion is NOT the omni that new fans should start with.
I know new readers like to start from the start but the thing is, H/S started with one shots and a mini and since they were one shots, the stories were fast paced and didn't spend much time developing the characters or the world they lived in, it just told the story of two people beating the crap out of slashers. And while I enjoyed those earlier stories, they didn't knock my socks off either. Instead what they did is they made me realize that if H/S became an ongoing it would have the potential to be something good. And that's exactly what happened when the first ongoing started, it delved into the psyche of the characters, it touched a lot on Cassie's sexuality and how it affected her, as well as her hang ups, it also dealt with Vlads loyalty to Cassie and just how far he's willing to go to save her. On top of all that, the world gets expanded in a big way, guest characters in the one shots become regulars that play an essential role in the book, and a handful of new characters are introduced.
In short, I recommend new readers to start with Omni 2 and then Omni 3 because thats where the "meat" is.