We are currently working to bring things like soft proofing, borders, and other features to Qimage One soon. With that in mind, a few thoughts...
Previewing print sharpness:
As Ernst and Bart pointed out, unlike sharpening at the editing stage, there is no way to accurately preview sharpening at the final printing stage. Diffusion (quality), media type, and other factors have too much of an influence there, so making a few small test prints to adjust sharpness is required. Once set, Qimage One will make sure that the chosen sharpness level is carried through to images of any resolution and prints of any size. Print sharpening should be viewed as a method to ensure that the sharpness of prints matches that of your monitor. Once you find that sharpening level for your printer and media type, it's "set once and forget" in Qimage One since it does all the calculations necessary to carry out the sharpening for any image/print size.
Soft proofing:
Soft proofing is coming, but be aware that it has similar limitations; I'm sure most people here are aware of this but thought I'd mention it. I use soft proofing on occasion to see how a particular profile/paper might handle certain bright colors or to get an idea of how D-max might differ on the paper. Getting a soft proof that looks exactly like the printed output depends on many factors such as print viewing conditions (lighting), two truly accurate profiles (both a monitor profile and printer profile), and it depends on the monitor being able to reproduce the entire gamut of the printer to name a few. As with most things related to photo printing, there is no substitute for making an actual print!
About driver previews:
While I'm on (or at least near) the subject, I thought I'd mention something that comes up occasionally. Sometimes we hear from users who say "my prints look too bright" or "my prints look pink" and we find out that they have checked "Preview before printing" in the driver and they are judging the print by the driver preview and haven't actually made a print. In the vast majority of cases, once we advise the user to ignore the color of the preview and make an actual print, they reply that the print looks great. Driver previews should be used to judge general print size and alignment on the page but not color. If you are using a printer profile, the driver is showing you "raw color" that has been profiled for the printer itself so it won't look accurate on the monitor.
Bottom line with all of the above, if you are printing on new/untested media or with a new profile or you are printing an image with critical colors, make some small test prints. Real prints are the only way to properly review output.
Regards