starter use

Somebody recently asked a similar question. I stand by my answer there: for many doughs, it's advantageous to start the final dough with a relatively large population of healthy microflora. When you feed a starter overnight, the yeast and bacteria within are "awake", so to speak, the next morning. Using a ripe levain will decrease the fermentation time for the final dough, which can lead to more predictable results. Pitching starter cold from the fridge will increase (exponentially!) the time that a dough has to spend fermenting, increasing one's chances of encountering unpredictable dough behavior.

I say "many doughs" because a baker could obviously be interested in longer fermentation times for the desired flavor and dough properties. For example, I gather from posts on this site that Ken Forkish is a proponent of long fermentation times, and thus his recipes often call for <10% prefermented flour. When I make pizza dough (from a Forkish recipe I got on TFL), I pitch a small amount of starter and let the dough ferment overnight. It's slacker and more sour, but that's ok for pizza. And plenty of recipes that call for "discard", like pancakes or English muffins, use an overnight ferment because gloppy, sour dough is just what they need. But my understanding is that for an average sourdough bread, one does not want to push fermentation too long, and thus benefits from the increased microbial power of a fed levain.

There are two camps, it seems. However, it's clear that one can make lovely bread using either method. 

The big advantage to using a (healthy, active) starter right from the fridge is it's less fussy and you can bake on impulse, when the mood strikes.

Some advantages to building a levain separately from the starter is that you can watch and see how long the levain takes to rise, and this will give you a hint as to how active your starter is and thus how long your bulk ferment may take. Remember that the bulk ferment stage is where the microorganisms are populating your dough. If you cut the bulk short and try to move on before your dough is fermented all the way through, you'll end up with sad underprooved bread. 

One other reason I sometimes like to build a levain is that I keep my starter with rye, and if I'm making a high hydration bread, that gooey rye makes the dough harder to handle. In this case I like to build the levain with hard wheat. 

The bottom line though is if you have a strong, healthy, active, reliable starter, you absolutely can toss a chunk of it straight into your dough. You can warm the water a bit if you're worried that the chill on the starter will impede the rise. Personally I find that kneading the starter/levain and the salt into the dough warms the dough up plenty. 

I have made good bread both ways, and failed bread both ways. Mostly when I fail it is because I build the levain and then forget about it and let it get overfermented and proteolytic and then it ruins the dough (turns it to goo). In this case I would be better off discarding the overfermented levain and going back to the fridge for a piece of mother starter instead. Of course, one can argue best of all would be if I would pay better attention and mind the timers I set....