Tried to write about this the other night but ended up deleting five attempts so just posted the title/question. A little clearer this morning and just wrote this reply kind of in response to comments. thought I might as well paste it here.
I like to have a clear plan for my practice so I don't waste time at 6 am deciding what to practice. it was my main problem with Vinyasa Krama and it's something about Ashtanga that suits me.
I'm not questioning the whole thing. However there is a kind of chemical reaction between certain potentialities in Ashtanga and aspects of my character that cause me to go down the route of .... over exuberant practice. I like the floaty kind of jump backs, the press to handstands, the lifting and flipping of 3rd. I'm drawn to the extremes of practice, Chakra Badhasana, tick tocks, the arm balances, strange, beautiful asanas. I find it challenging and love the problem solving aspect of a difficult pose.
But that said, that's not really how I want to practice my yoga. Gannon reports Jois as saying that 3rd is for Demonstration purposes and I can see what he means. The Arm balances are cool but taking up a third of the series seems absurd. It's fun, I can do that kind of stuff but it makes me pause and ask if that's how I really want to practice.
The Vinyasa Krama experience was quite powerful, less asana and practiced more slowly, strong breath and bandha focus, everything else stripped away. I tried to practice Primary and Intermediate in that manner but before I knew it I found myself working on tick tocks and arm balances again. It's not a criticism of Ashtanga but of how I end approaching it. It got me through the first couple of years learning the practice though.
It might be fun to practice like that occasionally, in the evening say outside of my regular practice but it's not the practice I want to get up for every morning.
The idea now is to practice Primary and Intermediate a couple of times a week in a simple, unflashy manner with Vinyasa Krama practices in between. Perhaps I'll work out my own Vinyasa Krama version of 3rd without the arm balance sequence.
Said farewell to the flashy practice in style with the Michael Gannon routine from his DVD. It's Sury's, Standing, most of Primary (up to bandha konnasana), almost all of 2nd and most of 3rd. Took him 66 minutes on the DVD without finishing, took me a little longer about 90 minutes (still not sure how I managed to do all 3 series in the time I usually take to do one). Strangely I didn't feel any more tired than after doing one of them, something about the vinyasa that carries you through. Found that interesting.
Tthose two approaches, focusing on the asana or focusing on the Vinyasa, both have their merits.
In the end surely it's about developing a personal practice, this has just been part of that process.