Yeah it's -promptsave. That did help, but it's still not working the way I want. Here's the more correct version:
minicap -save "c:\temp\screenshots\capture_$customdate$_$appname$" -customdate "$Y$m$d_$H$M$S" -sleep 2 -capturescreen -closeapp -exit
First, it's not saving files. If I use -promptsave then it asks me where to save and I just hit OK on that dialog and it works fine. But without the promptsave it won't do anything.
Second, there is a dot after the $customdate$ token, so it does "capture_20110815_092802_cmd..gif".
I'd expect the app to return an error if the filename isn't a valid filename, instead it just fails silently. Silent failures are bad usability.