Pro's: They cushion the impulses generated each time a cylinder making 800 hp fires like that found in a nitro car. The rods are relatively cheap.

Con's: They stretch at high rpms so piston to cylinder head clearances must be large. They have a very short fatigue life and wont last long in a car that will see a lot of miles. They are large and don't fit in small engine blocks well. Steel rods of comperable strength can be made lighter.

Aluminum rods have a very limited application and there are many reasons you don't see them used more often.