The problem with Frank is that he, in comparison, isn't as interesting because of the other two characters.
Having a main that actually wants to get out of the hood is pretty cool and such, but when you have an insane, gas huffing nutcase and a man with family issues, Frank's stuff is kinda pale.
That isn't to say what's there isn't interesting: his actions and hypocrisy, his interactions with his friend Lamar, the usage of money and staying true to yourself or changing for the better, etc. All that starts that the beginning of the game and just kinda peters off when the other characters get explored.
Suddenly, Frank is the voice of reason, and his own troubles are barely brought to the front like the others. They really could have done more with him, since he's a real good character that genuinely wants to change but doesn't know how.
I mean, the story balance is way off. Trevor gets some exploration, but it's not as deep as Michael, who the story seems to place as the main character, and I was hoping for something different when the game was first announced.
Edit: On another note, I can't wait for a patch. I'm really started to get angry at the lack of care put into the cop system. By that, I mean the retarded system of having peds call the cops on you if you stand too close to them, and by that, it's like a good distance away. Oh, and the cops need to stop freaking out and help me out once in a while. I pissed off three peds without harming them, and had a cop watch as I got pummeled, but the second I defend myself it's "STOP THIS IS THE POLICE". And another thing, if I help you take down a criminal outside the random encounters, don't fire on me. I honestly don't see how that stuff got through testing, or how reviewers kinda skimped on those details.