The 3-pass approach will make for a huge improvement in the final output, though it does add a bit of work - and thinking - along the way. I have to admit that I do 3 passes for prints only, and I stick to only a final SmartSharpen for web output.
I just got 4 20x30 test prints done - 1 comparing upsize methods, another comparing sharpening strengths, and 2 more comparing my upsize methods to the printer's RIP. Without going into details - I just haven't studied the prints enough - I am left with the conslusion that it's all about the sharpening.
Saturation is quite subjective, and probably the easiest to deal with and learn. If you have your monitor calibrated then chances are very good that your final print be fine, and probably perfect. To your eyes, and those are the only ones that matter really. And if you impose some limitations to saturation you should be fine in everyone's eyes.
Shadow and highlight detail are a bit trickier to learn. CS's Shadow/Highlights is wonderful and only a little difficult to learn. It's a little more difficult to get a grip on the printer's output of the blackest and whitest point, but most every printer (home or not) is going to deal with them very well. The upper end of printers - the pure CMYK printers - is much trickier but you'll know that when you use them. And all in all it's harder to mess up the printing of the blackest and whitest - if they're imperfect it's tougher to notice, or care. IMHO.
I'm currently of the belief that upsizing for large prints is necessary for proper sharpening, but easily done unless you're upsizing extensively. The test prints I did were upsized 216% and I don't see much difference between the methods. But they haven't been studied yet so I'll save my final thoughts, other than to say that I truly believe that sharpening should be done at the final output size, so thus I believe that upsizing is necessary.
But sharpening... Subjective, yes, but within limits. It's easily underdone and easily overdone. It's easy to do it with the wrong method - as you said when you found that Local Contrast Enhancement is not right for all images. And there's a LOT of methods. Sharpening on-screen is extremely difficult to master for a final print. Well, maybe not difficult but I think it takes a lot of experience to master. It's more difficult because of differences in monitors - not only LCD vs CRT but the quality levels of all the different brands in each. It's more difficult because of differences in printers - high DPI inkjet vs low-dpi, dye-sub, and LightJet-type. And throw in output for the screen, too. In my opinion all of the difference are fairly easily overcome by removing the differences - stick to one monitor on one computer and print to one printer. Once you get used to the 3 then they'll be no differences of the output, and you "only" have to be concerned with the differences in input.
Luckily the output sharpening can be done with simple formulas, as can the capture sharpening. So we're once again heavily concerned with only a single step, the creative sharpening. But how much sharpening should be done? What method(s)? How strong can you go? How strong do you like it? What about the background? Should it be sharpened at all, just a bit, or equal to the subject sharpening? And what about details, like eyes? What about the differing subject types? (Compare a portrait to a cityscape to a landscape to a furry animal. All should be sharpened very differently.)
So in my opinion, it's all about the sharpening. And darn it all, it's the most difficult thing to master in post processing....
and switched to a two-pass approach. After completing my RAW processing in ACR, I'd open the photo in PS and run local contrast enhancement as the first step in my workflow. This became my first action, and it worked very well for many photos. Eventually, I noticed that local contrast enhancement was great for landscapes but not very useful for many other kinds of shots. It sometimes added contrast where I didn't want it.
