FWIW, The + and * registers appear to behave the same on gvim for windows. I think * is actually expected to represent the system clipboard.
:help clipboard
Also another AWESOME tip , if you set an "a" among your guioptions, your visual selects and mouse selects automatically get copied to the * register.
: help quotestar
I realize that X environments mainly do this already, but not the visual select. Most of my editing is through SSH so I don't get to use the gui features much. The only time I use gvim is in windows, so it was pretty revolutionary for me.
Of course it only works for non-terminal vim. Someone may make it work on Mac though by leveraging pb{copy,paste} in some clever way (can't remember the X11 equivalent ATM)
I believe the special + register for the system clipboard is enabled by a compile option, but that may not be entirely accurate. I have Vim 7.3 installed via Macports and it works for me.
Yes, it's the "+clipboard" option (as shown by :version). If you weren't doing macports (or brew) already, the downloadable MacVIM version does include a "Vim" binary that's usable on the commandline. Somewhere in /Applications/MacVIM.app/... (can't check at work). Just symlinking or simply setting `alias vim='<path_to_binary>` works perfectly.