I run vim 7.0.158 (+multibyte, gui=carbon) on Mac OS X 10.4.8.
Utf-8 encoding is used both in files and in Terminal.
If there are characters with Unicode numbers over 0xFFFF in text,
they are displayed as question marks by vim (both in Terminal and in GUI).
But TextEdit and cat do display that characters.
To reproduce - insert something using Special Characters panel.
Do your results differ?
This problem has been discussed on the multibyte list
(for other platforms):
PS. Free Code2001 font has lots of "High Unicode" characters,
but Apple Symbols Regular have some in Deseret (0x10400 --0x1044F) group.