I'm not sure why the distribution is an issue with Purina but it IS.
I fed some of their product last summer and I'm running 3 different trials of my own right now, also using some of Purina's product.
I believe from what I've seen so far, they make a good high quality feed, fish seem to do well on it, but of the 3 Purina dealers here there seems to be issues getting it.
Purina management got me what I needed for the trials last year but if not for Optimal, I'm not sure what I would do as far as having a steady fresh supply of feed available.
I have an interest in experimenting with other feeds but as for needing and getting it, Optimal can't be beat.