I am sure this is not so as all that happens is you get the expected subtle changes in colour. Soft proofing in CS3 with paper simulation is a much more dramatic change.
Interesting. It does simulate paper, although it is not in your face, in the main window. When you select your paper/printer profile in the print dialogue, you will see the change in the small image, and if you do a preview you will see it very clearly (correctly) as washed out if the paper is a matte like Hahnemülle Photo Rag. Then it is as dramatic - to my eye - as having the paper option simulated in Photoshop.
Here are two screenshots, where the difference should be different enough to see, of the Aperture window softproof but without paper correction, then Preview (pdf) with it, generated from within the print dialogue
In photoshop I tend to do adjustments to the soft-proofed version with a non-soft proofed version also open, and that is not easy to do in Aperture.
I usually use Lightroom > Photoshop softproofing with Photokit Output sharpener. So Aperture does have the three stage sharpening of Photokit (two stages in the Adjustments window (pre and creative) and one in print - so it also scores there against Lightroom. If I was going to use Aperture regularly for printing, I guess I would make up a test print page of each paper with a compilation of the same image with various levels of print sharpening applied, so as to choose the right combination.
I'm not sure I could say I am in love with Aperture - but I am working a lot with iWeb for a client at the moment, so I thought I would give it a go as the integration is rather neat . . . and my throat is getting less sore than in the first few days that I used it . . . nevertheless, the usual stumbling blocks for switching over for me . . . can't read my keywords in sidecar files, no ProPhoto RGB, (and for me) no colour fringing lens aberration correction. I did discover that iWeb was uploading half size previews of images rather than the actual jpg files (I had set max size of previews to 50% of originals, and all my uploads were half-sized - corrected by selecting another option. All my images are stored outside of Aperture (another inelegant stumbling block, as I'd need to use more than one hard drive). A noise ninja type option is the only other major item missing, and I noticed that lightroom was picking up pixel hotspots in this image that Aperture does not correct for
On the other hand, I have some very difficult images to work with, and have been pulling them around without mercy, without getting some of the fringing artifacts of lightroom, so kudos to Apple there - if you are 'just' a lightroom user, Aperture is a very serious alternative, it seems to me.
(for info - I do my own paper and screen profiling with EyeOne, and images from screen to paper are WYSIWYG and 100 percent trouble free - quite amazing, really (and so it should be for the price!)