I generally agree with this guy but I think the plot is an improvement to the previous games.
I never really connected with Tommy and found CJ to be annoying (vehemently anti-drugs "cos they mess people up" but kills people at the drop of a hat ..... yeeaahh). I actually felt empathy for Niko, he was obviously a normal guy before the unnamed war messed with his head and he tries to put that life behind him, albeit whilst gunning half of liberty city
The main plot bit I liked was the bleak ending, it wasn't a masterpiece of writing but it annoyed me less than the "you are the master of everything, congratulations" endings of VC and SA. I do prefer the ending to III though simply for the comedy value as No Name blows away the annoying chick in the end credits.
What did confuse me was how Ninko kept whining about how poor he was after he'd robbed a bank and got away with a shedload of money. Didn't like the choice think because all of them except the last one had no real effect on the game, although this may be because I had been playing mass effect just before I bought GTA:IV