I tend to be in the starter camp myself. I use both Jamil's calc and the one at yeastcalculator.com alternatively to get an idea of growth rate, pitch rate, etc. based on the beer I'm making. There are just too many things in the supply chain that can impact viability of the yeast (heat, handling, age, etc.)
I've had very few "duds" from White Labs over the years. They're a great company with a superior product. But that being said, I have had a couple of them. And in each case my starter regimen allowed me to find out I had a clunker before a put 5-10 gallons of beer at risk for a poor fermentation.
Ferreting out bad/dead yeast aside, pitching rate matters. At least it has in my end product. I get better attenuation and a significant reduction to full elimination of any undesired flavors and aromas when I pitch a properly-sized, fresh, active starter for the beer I'm brewing. Well, that plus proper temperature control.
I've had a few one-on-one discussions with Jamil and a handful of other pro brewers. Across the board, each of them has taken the time to convince me that fermentation is where the distinction between good and great beer lies. Pitch a proper amount of healthy yeast and design your temperature schedule with your end goal in mind, and you've won a large part of the battle.
As Jamil points out, a starter is cheap insurance and proof of viability. Additionally, I can make a starter that will ensure I reach my desired pitching rate, often decreasing the amount of pre-packaged yeast I have to buy.
For less than $100, I purchased everything I would need to make canned starter wort. With a pressure canner and a couple of packages of both pint and quart canning jars, I can make up several jars of canned wort in an afternoon. I usually buy a 3# bag of DME and just make cans of starter until I run out. In a couple hours, I have enough shelf stable starter wort to last me several batches of beer. That takes the process of making a starter down to about 10 min when I am ready to start propagating prior to brewday. I just grab an appropriate # of jars of room temp wort, sanitize my flask, dump in the wort, hit it with a little O2, pitch the yeast and pop it on the stirplate.
The night before I brew, I put the finished starter in the fridge to cold crash. When I start my brew session, I decant the starter, give it a pint of fresh starter wort from one of my jars and place it in the fermentation fridge at my desired fermentation temp.
By the time I am done chilling my main wort, the starter has already woken back up and is actively fermenting. I let fermentation go at my desired temp until things begin to slow down. Then, even with ales, I ramp my temp up by 1F per day or so until I am about 3-4F above my main fermentation temp. Using this process, I've had great results in terms of attenuation as well as hitting my desired flavor and aroma profile.
Getting this involved with the process is not for everybody. But for me, I like what I've been tasting since I started spending more time focusing on the fermentation side of things. Direct pitching a White Labs vial will, in almost ever case, make beer. I've even used the direct pitch process to make some really good beer.
But increasing pitch rate and controlling fermentation temps makes better beer for me every time (unless I do something stupid that has nothing to do with pitching rate or temp control)
