Forms can be useful...but as everyone thinks they know best, they will never expand their understand.
Robert is correct in IMHO that you transend form and need to do the real thing wheather.... sex or fighting.
To me, its very useful doing air dummy as its different from on the dummy. most kung fu systems have forms which allow full motion, flow and body cotnrol, air dummy is a good answer to that.
I like returning to the forms although I know them and teach them all the time. I find they provide mental training and a return to basics, elbows, strucutre etc.
I say do what is difficult, forms are easy great move onto sparring, air dummy is easy move onto somethign else, one legged stance is easy, move onto something else....if its difficult for you to do it might be worth doing it more.
Paul
www.moifa.co.uk