I often use Smith's amidol formula for enlarging. My usual process for a mixed session of enlargements and contact prints (which is often the case) is to mix up a tray of the Azo formula, print the Azo prints, then add the requisite amount of KBr and benzotriazole to convert it to the enlarging formula.
For some papers it doesn't do much (like Ilford MGIV FB and RC)--maybe a little bit more density in the blacks, but that might be achievable in Dektol with a longer development time. But, if I have a tray mixed up for Azo and I have some APUG postcards or some such to run at the end of the session, there's no reason not to get a little more use out of the amidol.
For Cachet/Maco Expo, which is now being sold as J&C Exposition graded and Efke Emaks, it's really nice--significantly richer blacks and the added advantage of water bath processing for intermediate contrast grades.
Steve Anchell was also an advocate of Expo and amidol, but I'm not sure what formula he was using. I think the principle is that the older style soft emulsion papers are said to respond more vividly to amidol and other chemical manipulations like warm and cold tone developers, auto-toning developers, and toning in general.