@triumvir: Omni always gets great sets. Too bad he's still trench tier and niche as fuck and gets like no playtime.
My crew of dota buds and I sit around 2500-3500 mmr. I've found Omni fairly effective, at that level. More importantly, I just think he's super fun to play, as I love playing support. (Barring obvious team comp faux pas) if I like a character, I'll play them. I still play Windrunner all the time, for example, despite the fact she's underpowered right now. I enjoy her playstyle.
EDIT: RE Carry-Omni: if he get's fed and ignores what the normal core items are in favour of stuff like Basher, Mjolnir, Helm of Dominator or Armlet, he can do an okay semi-carry. He's already tanky and durable, with a built-in BKB. It's sort of a joke build, but I bet someone could make it work.
Aw yeah. Let's talk about sick doto pocket strats in these GB comments. Everyone will know what we are talking about.