I've been using a color management workflow that has worked for me over the past few years, with CS2, CS3, CS4 and now CS5. I've been using an NEC 3090 for about 3 years now, calibrated/profiled by the eye-1Display ii, and more recently, by the Colormunki, both with the Spectraview ii software. I print from Qimage on a Win7 computer, to an HP Z3100 gp PS printer and use a Just Normlicht print viewer with adjustable brightness.
I have been softproofing in Photoshop using either Perceptual or Relative Colorimetric rendering depending on the image, and I have always checked the Simulate Paper Color box. I duplicate the image and have them side by side, using adjustment layers to bring the softproofed version back as much as possible to resemble the optimized but not softproofed version. My results have been quite good.
A few months ago, X-Rite guru Joe Brady said he does not use Simulate Paper Color for glossy or luster papers, but only for matte papers. In my usual manner I scoffed to myself. Today I decided to try it, using Epson Premium Luster. I am astounded at the results! It took less adjustment on the softproofed image to bring it into line with the original. More importantly, the softproofed version resembled the final print even more than had the version softproofed with Simulate Paper Color on! It seems that much of my adjustment in the past had been to compensate not so much for the paper, but for the changes caused by the Simulate Paper Color option!
Is it possible that the Photoshop Simulate Paper Color somehow is not as accurate as it is supposed to be, perhaps using an outmoded algorithm?