with so many options and tools to acheive the same or similar effects using Photoshop, i'm just wondering how the pros here view doing things the "short" way?

like sharpening or converting an image to black and white- with sharpening, you can do all sorts of things with the channels, modes, etc and supposedly come out with superior results- but with many images, i just dont see that its worth the extra effort.

if i were to apply for a job doing this for an agency of some sort, how much emphasis would be placed on doing things to such a degree vs. just using the more common techniques?

I'm not really a pro, but...

Converting to black/white -- my "short" way is always to use the Channel Mixer. But if I'm aiming for "short" I won't necessarily play around with it the way I would if I were doing it the "long" way, and I won't use multiple layers. Generally I'll have a quick look at all three channels, and based on that will decide roughly what percentages of each I want to use.

Sharpening -- my "short" way is to use Unsharp Mask with Scott Kelby's recommended starting points for different types of image. If I'm happy with that then I won't do anything else. But the other techniques do have their place, particularly Lab or Luminosity sharpening (and you can always have these recorded as actions so they don't take long to do) -- plus if restoring an older photograph (as opposed to retouching work) more complicated techniques like smart sharpening tend to be useful.

I suspect it would depend on the type of agency, but that the most important thing is being able to judge whether a "quick fix" will work fine for a given image or whether it will repay getting more fiddly -- partly that would depend on the brief you got with the job although some agencies would be more likely to place themselves at one end or the other of the scale. You don't want to take on a three hour job for a ten minute fee, but you may be unlikely to get away with doing a ten minute job for a three hour fee.