Simulator printf needs setup?

I'm trying to use printf() on uVision4 in Simulation mode. The code runs or steps fine in the debugger but the "Debug (printf) Viewer" doesn't show anything. Was I wrong to assume that it should "just work" whenever the configured device has a S*OUT VTREG?

The manual doesn't explain much, which led me to believe it should work. I'm mostly looking at a NXP LPC1769 but really any Cortex-M3 would do for now. Did s0time = 0, and here's the start of ASSIGN and excerpt from DIR VTREG resp:

assign
  WIN: <S0IN >S0OUT
 WIN2: <S1IN >S1OUT
 WIN3: <NUL >NUL
 COM1: <NUL >NUL

        S0IN: ushort, value = 0xFFFF
       S0OUT: ushort, value = 0x0000
      S0TIME:  uchar, value = 0x00
      S0BAUD:  ulong, value = 0x00002580
        S1IN: ushort, value = 0xFFFF
       S1OUT: ushort, value = 0x0000
      S1TIME:  uchar, value = 0x00
      S1BAUD:  ulong, value = 0x00002580

Also, the value of S0OUT in the watch window doesn't change; should I expect it to show the transmitted characters?

Cheers