The 'test track' uber-version (whatever the long and twisty one is) is pretty much 3 minutes and 54 seconds of cornering at various speeds. Which is damned fun, if completely unforgiving. Don't zone out and interface with a wall at 60 mph. And if you do, whack the handbrake before impact so you mess up your rear bumper rather than your engine. Forza doesn't do day/night, and no one's gonna pull you over for a busted tail-light.
Factory Spec races may be my favorite category, since everyone drives the same exact vehicle; it's a pure test of skill. Mind you, part of the reason I got hooked on this damned game to begin with was the endless gearhead mischief one could attend to, so I suppose that makes me a hypocrite. That said, trading in your Viper Competition Coupe for a Porsche 914/6 is like playing in slow motion. Non-instantaneous gear shifting? An engine that takes a second or two to hit 6k RPMs? What is this malarkey? If anything, it's a vacation. The Porsche's got some rear-end slip, being RWD and all (more so with TCS and STS turned off), so it feels a hell of a lot like the Comp Coupe, just more sluggish. Since everyone drives the same car, referencing the fastest runthroughs on the scoreboard is a great 'cheat sheet' if some turn is kicking your ass (end serpentine on Silverstone, I'm looking at you). The guy that holds the 914/6 record on Silverstone has a bad ass Mondrian paint job. Check it out.
Why didn't I take up Manual transmission earlier? If anything, it adds a whole new level to vehicle management - far from being 'same as automatic, but you have to press buttons', gear-shifting becomes highly tactical, and a reference point for turn tactics - "downshift from 4 to 3 and ride it here; slide through and follow the tach up there; enforce diminishing turn radii in serpentine by taking final turn at 2;" that sort of thing. Made of win, it is, and a great inoculation for 'straightaway hypnosis.'