The product I use depends on where the car came from, straight from a dealer or used.
For used cars I've had very good luck with meguiars 3 step wax. This is a cleaner, a polish and finally a wax. Its very long lasting and does wonders to bring your paint back to life.
For new cars these one step quick products seem to produce good results - as they should - the paint is clean, new and free of swirl marks.
I personally would suggest that you say away from the one step easy on/off products unless you can repeat this process every 3/4 months. Not to say that these cant last longer but if you dont (or cant) give your car lots of attention you'll get more mileage out of more traditional products.
Also keep in mind that all the nice folks providing information here live in different areas and face different day to day conditions so that effects the results they get out of the products reviewed here.