I started watching iZombie about a week ago, binge-watching on Netflix. The first episode was great: Introduction of characters, humorous mannerisms and situations, but also the introduction of a more serious central plot.
The show handles both funny and serious situations well, the dialogue is good and the actors are fantastic in their roles.
However, the writers are sloppy/lazy in resorting to clichés to keep the show moving from week to week: First, you have the device where the main character has a secret that she cannot share with anyone, thus leading to all the opportunities one could ask for to create funny or "dramatic" situations. Sure, at first one could understand that Liv could be terrified of her condition, and afraid of what might happen should her family, loved ones or public find out about her condition. But that only holds up for a few episodes. It becomes clear after one gets to know Major that you realize she could have explained to him that she'd contracted a condition that was contagious, and that prevented her from having the contact or experiences a full life demanded. Instead, she keeps her secrets and as the series progresses and Major begins to find out that strange things are going on, she continues to hide the truth, even though he's getting into a dangerous situation. And that's only one example.
Another problem is Liv's tendency to take on the personality of people who's brain she eats. This is only true insofar as it serves the plot. For example, as a radio talk show host she becomes an insufferable bitch psychoanalyzing every man she knows, almost to the point of ruining a friendship. However, when she has the opportunity to eliminate a zombie murderer/drug dealer while "possessed" by the personality of a sniper, she decides at the crucial moment that she isn't a killer. Sure, she has no alternate plan for stopping the thug from continuing to murder people and sell their brains for profit, but she passes on the chance to end this blight on the human (and zombie) race. As a result, her boyfriend, also a zombie, is murdered.
Basically, the writers use a lack of communication between Liv and others, even when it would make sense, to create tension or humor in the show, and her ability to absorb personalities and see their memories is a deus ex machina that allows crime cases to be easily solved, often leading to humorous scenes as well.
Most people will enjoy watching iZombie, but if you were weaned on "smart" shows with Emmy Award-winning writing, I doubt you'll stay with it for long. And you shouldn't: there are plenty of brilliant, quality shows to see, and there's no need to waste your time on the bottom 50%.