I think the world of CFL is just starting to take off - they are good if you only have a small space to grow.

If you have a decent amount of room MH for vegging and HPS for flowering will give you a considerably larger yeild / better quality bud than CFL's will, but CFL's can be used to grow from start to finish.

The main rule with CFL's (so ive heard) is to double the wattage when you start to flower - otherwise the yeild will be very small.

Also CFL's are great for starting a seedling as a high powered MH / HPS would be too strong at first for the plant.