At the moment, counters are particularly an issue. First of all, they seem to start at 0. I've programmed in C and Basic, but for identifying my photos, I do NOT want them to have names like "ddb 20100701 010-000-orig.NEF"; that "-000-" in there is a problem, it confuses people. And that's what I get when I rename with FPV right now using counters.
Second of all, I can't find any explanation of what the three different kinds are.