Nothing new is introduced after this point, just refinements to what you have learned. Chapter 5 give you more characters and teaches you how to fight well, but it is broken up with many unskippable cut scenes, and mostly works as color for the next chapters of Vito's story. Make sure you get the magazines in the prison, you will not be coming back her again, ever.
Chapter 7 has you out of prison, you meet up with Joe for a night on the town and a refresher on driving. You get a new apartment, where all the cars you had before going to prison are still parked, along with whatever upgrades you gave them, and generally get back on your feet. I like to steal a few cars to get some cash and stock up on guns; make sure you visit Harry here as, although you can revisit the store anytime you want, there is a magazine present here at this time that will disappear in future visits, its your one chance at getting them back. Protip: I like to stash a cheap car in my garage before I go to prison, then drive it to the junk yard for quick cash, but this is not necessary, just an easy option.
Chapter 8 gets you into the seedy underbelly of Empire bay. You meet up with some old friends and have a pretty solidly done shootout. At the end of this one you find that Derrick is a car exporter, allowing you to steal high end cars for some truly excellent cash returns (this is another thing I didn't realize at first, I had no idea I could do this repeatedly until several missions later)
Chapter 9 is where you get made. Make sure you have a good upgraded car, you'll need to be fast to keep up in the chase scene, and it would be a good idea to make sure you have both guns and ammo before heading out . At the end you'll be gifted a pretty sweet car which is starting to rival the ones given by the special editions, especially with the upgrades.
Chapter 10 is among my favorite game missions, ever. Rarely has anyone managed to build tension like this while managing to keep the action moving. This mission represents the apogee of Vito's career, nothing is quite the same after this. Sidenote, this is also where I figured out I could take cars to Mike's crusher for profit.
Chapter 11 is where Vito's life gets messy. It starts off with a time race mission which you are unequipped for (you need a fast car and have to steal one) and ends up with Vito needing a big score . The final leg of the mission has some great shoot outs and a decent car chase, but the real star of this chapter is the bleak direction of the story.