Hi,
First, PM is a great piece of software and I use it all the time to manage my photographs. I use Nikon DSLRs, working in raw all the time. PP is split evenly between Capture NX2 and Photoshop CS3.
There is one additional feature I would find very helpful: I alternate between colour and black and white work, and it would be great to have a quite way to preview a raw image in b&w. I can't always judge whether a picture would work better in b&w, and a way of toggling (even if it's only to desaturate) would give me a quick idea before importing into an editor and going through the necessary steps there. Doesn't have to be anything complicated, but it would save me quite some time each week. I'd pay a small premium for this.
Thanks,
Hugh