I can't comment on the Sharpmaker from experience, but my good old Lansky kit is fine and I think it may be a bit cheaper (grit not diamond)... Sharpening freehand on an oilstone is a serious skill that you only get after wrecking lots of knives.. If you only have good knives get a Lansky or similar, money very well spent!

My SS4 had a very obtuse grind when I got it and it wouldn't cut at all. Even the sandpaper trick didn't do anything. It's now set to an 'inclusive angle' of 50 degrees with a V grind (Lansky) and is hair popping!