Yes, i think number one priority is good soil and right sowing date,
Perhaps the biodynamic calendar is more a potentiation of personal intention , which maybe is more important than actual astrological circumstances , who knows?
If it works on an astrological level then great! If it works because it catalyses the gardener to focus on sowing on a deeper level then also great! If it is a useful calendar then great! etc
Interesting questions arise from the interaction between gardener and plants –
http://www.masaru-emoto.net/english/water-crystal.html
plants and indeed ourselves are mostly water!
As it happens i sowed my broad beans on saturday, a flower day – but it was a convenient time for me to do the sowing, it was dry so i took the opportunity! 
and most importantly i was happy doing so!