My $.02, based on my own experience.

If you have a 4-channel airplane (airlon, elevator, rudder, and throttle) can you still fly without using the rudder?

Yes & No... Even the most novice pilot has to learn how to use the rudder during takeoff and landing because that is usually the surface that is also attached to the nose wheel or tailwheel. Even if you have no steerable wheel on your plane you need to steer using the rudder, i.e., you need the rudder to steer the plane on the ground.

Can you fly without the rudder after its in the air. Abosolutely yes and most novice and some moderately experienced pilots forget there is a rudder, not a problem if all the're doing is flying simple patterns and acrobatics.

I didn't learn how to apply the rudder in my flying until I had been flying for almost a year. I was constantly aware that one day I needed to start using the rudder if I was to get much better.

What do you use the rudder for?

1) When your lining up your airplane for a landing the rudder helps to point the nose at the runway without having to bank the airplane, something you don't want to do if your already close to the ground.

2) Coordinated turns require the rudder and helps to turn the airplane in the air without loosing or gaining altitude.

3) Knife edge maneuver -- can't do without significant rudder control.

4) Stall turn -- also can't do without significant rudder control.

5) Controlled spin -- need rudder and elevator (You could use the airlons here but your spin would actually be a diving axial roll and your airplane will loose altitude much faster than it would with the rudder.)

6) ETC!!!

You can spend a lot of fun flying without using the rudder and for some I would recommend that you don't try to add the rudder to your normal flying until you are very comfortable with flying -- just one more control you don't need to be confused by while your trying to learn how to fly.

The diahards will say that you MUST learn how to use the rudder at the outset or you will develop bad habits -- RUBISH. You have plenty of time later on to integrate your rudder and not have to worry about it confusing you initially.