I baked my first ciabatta today! I followed Daniel Stevens' recipe in River Cottage Handbook No. 3: Bread.
In an ideal world, I would have made this completely with my own sourdough starter, but, being short on time and not being able to give my starter the full-time attention it needs, I make do supplementing my starter with commercial yeast (Lowan's dried yeast). Indeed, Stevens' recipes are all based on commercial yeast and, for best results, he recommends adding a good "glug" of your own starter (which I do).
I omitted the oil from his recipe as I read that oil makes it less chewy: http://sourdough.com/blog/
The crust was certainly crunchy, chewy in the middle, nice big holes, great doughy texture.
Flours in my starter: started with wholemeal spelt, rye and then spelt. Gave the ciabatta a pleasant sourness.
Flours in the ciabatta: 750g Laucke baker's flour (wheat) + 250g semolina