A lot of people have complained that Marvel's Agents of SHIELD is disappointing because it doesn't really feature Marvel characters. Well, let's see. After 8 episodes, for the record, here are the characters that were featured both on the show AND in the comics (excluding flashbacks to movie footage, like this week's Thor referencing).
So to date, seven actual Marvel characters, though others are somewhat inspired by Marvel characters (there's a Luke Cage type in the pilot, a Asgardian in The Well, Centipede sounds like a down-market Hydra, and its been suggested a mysterious character was actually the Fixer). I don't know that it would help the show if they had less obscure characters making appearances, but it's certainly playing a long game so as not to upset the movie cart. If it survives to a second season, we might actually see - gasp! - costumes! But I'm not holding my breath that long.