Not my own review, mind you, but one by my good friend Jacob, who runs a YouTube channel called In The Works Media. (For all you gamers out there, he specializes in video game reviews -- something I know very little about.)
He does a good job of laying out the plot and pointing out some of its high and low points.
I agree that Machete strikes a good balance between contemporary politics and vintage grindhouse fun. I will say, though, that it's not on the same level as Planet Terror (2007). At times, it feels like there are too many bad guys filling the same role. The plot becomes a bit more complicated than it ought to be, with several characters suddenly changing directions for no real reason. In my opinion, the experience could have been improved by playing down the plot.
As you might expect, the best way to watch Machete is just to turn off your brain and enjoy the ride.