somehow, apple managed to really screw up the X11 implementation that they shipped with leopard.
fortunately, they had really sharp guys tracking this and the xquartz project stepped in quickly to plug the gaps. if you’re running leopard, this is the release to get. personally, i keep a copy of the latest version on my machine in the odd chance than an OS upgrade happens to trigger nastiness on the X11 front.
why use this versus terminal?
if you need to run a UNIX X app, you’re going to need an X server running. however, for the most part, if you’re just doing CLI stuff you’re not going to care. i happen to have an apparent inability to use the option key as meta. terminal doesn’t allow you to remap the command key to meta so .. i use rxvt (built from ports) and xterm is obviously readily available. X11 will honor the use of the command key as meta so my thumb will do the right thing.
make sure you’re using something later than r2.3.2.1
release 2.3.2.1 and later provides the ability to update the system pasteboard w/copy on select from X11. this means that copy and paste work pretty much the way you would intuit between OS X apps and xterms, etc. without having to manually invoke the copy operation from the menu w/i X11. this of course assumes that you have sanely disabled “Enable key equivalents under X11”.
note to make this work you need to enable the “update pasteboard immediately when new text is selected” option in the preferences. this has persisted across a number of releases and pretty much just works the way you want it too. this was a major nit for me for a number of years. if you’re a recent convert, enjoy.