not to dig up a semi-dead thread, but I just purchased three stones (medium, fine, and ultra fine grit) from Spyderco.
I have three words.
Ho. Lee. $hit.
I've never been very good at sharpening knives just with a stone, and it turns out it was all in my equipment and not my execution. I took Franciscomv's advice and worked on a few kitchen knives to get the hang of it, and I was highly impressed with the edge that it put on my knives.
Now, my Centofante4 has a nice straight-razor like edge so the entire cutting edge was nicely sharpened. I still cant quite get the upswept tips on my kitchen knives as sharp as the rest of the blade, but I'm working on that.