After my abortive attempt about a year ago to get hooked up with a Cessna 172 to fly, I am now in the process of checking out in another one. I flew one with an instructor the other day. I didn't get signed off, but I should be able to in the next lesson.

That isn't me flying, by the way, this is me on the ground taking a photo of the same 172 taking off.  
Interestingly, this particular airplane has a feature that I've never seen in a small aircraft.  I think every other one has had a battery master that was a toggle (in the case of older airplanes) or else a rocker switch.  This one has a plunger that you pull:

One thing I didn't do in my training flight was turn on nav lights (like "parking" lights in a car) or the collision beacon.  I'll have to work on remembering that.  

As I mentioned in my earlier flight, the elevator trim becomes far more important in the 172, because it has much greater elevator forces:

At the bottom of that same photo is another big difference from the 150.  The C-172 fuel selection can select either of the main fuel tanks, or both, wheras the 150 is just on/off.