I have been to many qigong retreats with other teachers and always feel them to be much more powerful in a seminar then with stand-alone practices.
One of the reasons is that I am highly kinesthetic and as such have a strong awareness of my body.
I have tried the active exercises in the Spring Forest system twice now and certainly find it to be a powerful practice. Every form I have tried has a different feeling and flavor of energy. Playing with the life force certainly is fun.