All:
16-bit screensavers are referred by their filename (a custom function that reads every single .SCR file to scan for "SCRSAVE :" will be needed)

Win9x:
Unicode support may slowdown performance (a delay of >3secs starting the other screensaver)
If "(None)" is selected then the password prompt won't work (needs support for /a switch and handling "password change dialog" via MPR.DLL)

Win95:
The "Test" button on the Windows control panel stops working if "(None)" is selected, open config of any screensaver to fix that
Broken Unicode support (you will get an error message about that)

Win7 and newer:
Rather pointless, seems to lack support for HW-Profiles. (Does run fine and SysWOW64 is used as 64bit System dir as it should)
Sidenote: The name of the "dummy" profile on the German Win7 is not translated