Another +1 for NSIS with older / elderly customers. I've also had success in that respect, and the NSIS support for custom DLLs let me extend NSIS to improve usability. (My products have to be installed in the plugins folder of dozens of different commercial programs, the DLL support lets me detect that automatically for my customers.)

I also like InnoSetup, and its Pascal scripting is certainly more straightforward than the NSIS Assembly-like coding, but NSIS has served me very well.